https://laohand.com/index.html New and updated developer command cheatsheets — Docker, Kubernetes, Git, Linux, databases, languages and more. Find fast, copy directly. zh-CN Wed, 26 Aug 2026 00:00:00 GMT https://laohand.com/guides/coding-agents-prompt-engineering.html https://laohand.com/guides/coding-agents-prompt-engineering.html Getting a coding agent right on the first try is not about the model but the instruction quality. This guide explains context constraints, minimal-change rules, test-first practice and review prompts, so you can craft reproducible prompts with fewer hallucinations. Sun, 06 Sep 2026 00:00:00 GMT ai-prompt https://laohand.com/guides/claude-code-real-workflow.html https://laohand.com/guides/claude-code-real-workflow.html An AI coding assistant is not "let it auto-fix" but a disciplined workflow. Using a real project bug, this guide walks the full loop from reproduction, adding a test, surgical fixes, to regression verification, with the exact instructions to issue at each step. Sun, 06 Sep 2026 00:00:00 GMT ai-cli https://laohand.com/guides/prettier-eslint-config-guide.html https://laohand.com/guides/prettier-eslint-config-guide.html Prettier handles formatting and ESLint enforces quality, but when their rules overlap they fight each other and pre-commit runs get messy. This guide explains how to divide responsibilities, turn off conflicting rules, unify config, and enforce everything in CI. Sun, 06 Sep 2026 00:00:00 GMT config https://laohand.com/guides/environment-variables-dotenv.html https://laohand.com/guides/environment-variables-dotenv.html Secrets in code, environment variables drifting across environments, and .env committed to git — almost every project trips on these. Following the 12-factor principle, this guide clarifies precedence, injection methods, and how to manage local and CI config safely. Sun, 06 Sep 2026 00:00:00 GMT config https://laohand.com/guides/vscode-debugging-launchjson.html https://laohand.com/guides/vscode-debugging-launchjson.html Compared with sprinkling console.log everywhere, debugging lets you pause and inspect the call stack and every variable at each step. Starting from editing launch.json, this guide gets Node and front-end projects debugging, then walks through the sidebar, watch expressions and conditional breakpoints. Sun, 06 Sep 2026 00:00:00 GMT devtools https://laohand.com/guides/tmux-session-management.html https://laohand.com/guides/tmux-session-management.html One dropped SSH and a half-run build, open files and a dozen panes are all gone. This guide shows how tmux named sessions, detach/attach reuse and window/pane layout let you reconnect after a network drop and pick up exactly where you left off. Sun, 06 Sep 2026 00:00:00 GMT devtools https://laohand.com/guides/mysql-index-design-explain.html https://laohand.com/guides/mysql-index-design-explain.html You keep adding indexes yet slow queries do not go away — that usually means the indexes themselves are misdesigned. Starting from real business SQL, this guide covers composite index column order, covering indexes and index-failure scenarios, then walks through EXPLAIN output section by section so you can actually read a plan. Sun, 06 Sep 2026 00:00:00 GMT db https://laohand.com/guides/redis-cache-thundering-herd.html https://laohand.com/guides/redis-cache-thundering-herd.html When your API suddenly slows down or your database collapses, three kinds of cache faults are usually to blame. This guide uses realistic log symptoms to help you tell apart penetration, breakdown and avalanche, then lays out practical defenses including mutex locks, null-caching and never-expiring hot keys. Sun, 06 Sep 2026 00:00:00 GMT db https://laohand.com/guides/postgresql-slow-query-tuning.html https://laohand.com/guides/postgresql-slow-query-tuning.html Slow query tuning is a three-step ladder: find the query, read the plan, tune the config. This guide covers enabling the slow log, telling Seq Scan from Index Scan in EXPLAIN, and the core knobs that give the best bang for buck on buffers and concurrency. Sun, 06 Sep 2026 00:00:00 GMT db https://laohand.com/guides/mysql-backup-and-restore.html https://laohand.com/guides/mysql-backup-and-restore.html Exporting with mysqldump is easy; the hard parts are whether the dump restores cleanly, whether the restores fast enough, and whether an accidental delete comes back. This guide covers consistency flags, single-transaction isolation, import-acceleration knobs, and a binlog-based recovery flow. Sun, 06 Sep 2026 00:00:00 GMT db https://laohand.com/guides/curl-api-debugging.html https://laohand.com/guides/curl-api-debugging.html curl is the first scene of most API debugging; this guide starts from "see exactly what a request sent", covering GET/POST, query vs body, Bearer/JWT auth, Multipart uploads, and reading status code plus timing from one response. Sun, 06 Sep 2026 00:00:00 GMT web https://laohand.com/guides/ssl-cert-auto-renewal.html https://laohand.com/guides/ssl-cert-auto-renewal.html Manually requesting a cert is easy; the hard part is renewing it before expiry automatically. This guide walks certbot through webroot and HTTP-01 validation, configures renewal on port 80, and pairs it with two fallbacks so missing a renewal still does not take the site down. Sun, 06 Sep 2026 00:00:00 GMT web https://laohand.com/guides/nginx-reverse-proxy-setup.html https://laohand.com/guides/nginx-reverse-proxy-setup.html Misconfigured proxies usually come down to location matching order and trailing-slash traps; this guide corrects the most commonly botched configs line by line and walks you through wiring a real Node backend into a load-balanced reverse proxy. Sun, 06 Sep 2026 00:00:00 GMT web https://laohand.com/guides/linux-file-permissions-guide.html https://laohand.com/guides/linux-file-permissions-guide.html From bit permissions to ACLs to why setuid exists, this guide clarifies exactly how read/write/execute are computed, when the special bits backfire, and why sudo should not be a blanket ALL—plus a safer habit before you break something. Sun, 06 Sep 2026 00:00:00 GMT sysops https://laohand.com/guides/systemd-service-debugging.html https://laohand.com/guides/systemd-service-debugging.html systemctl is-failed is just the first step; this guide splits failures into four kinds—launcher error, process instantly exiting, dependency not ready, and port never listening—with the right log entry and fix for each. Sun, 06 Sep 2026 00:00:00 GMT sysops https://laohand.com/guides/linux-network-troubleshooting.html https://laohand.com/guides/linux-network-troubleshooting.html From unreachable pings to crawling slowness and flaky domain resolution, this guide walks layer by layer—link, IP, transport, application—showing which command and which field to look at, with copy-run experiments along the way. Sun, 06 Sep 2026 00:00:00 GMT sysops https://laohand.com/guides/linux-memory-oom-hunting.html https://laohand.com/guides/linux-memory-oom-hunting.html When a server claims it is out of memory it rarely tells the whole truth; this guide shows how to use free, /proc/meminfo, cgroups, and dmesg to close in on the process actually eating memory, and how to configure against recurring OOM kills. Sun, 06 Sep 2026 00:00:00 GMT sysops https://laohand.com/guides/python-packaging-guidance.html https://laohand.com/guides/python-packaging-guidance.html For turning scripts into publishable packages: pyproject.toml for metadata, venv isolation, lock files for reproducible environments, and releasing to PyPI with twine. Sun, 06 Sep 2026 00:00:00 GMT language https://laohand.com/guides/javascript-error-handling-patterns.html https://laohand.com/guides/javascript-error-handling-patterns.html A practical catalog for backend and full-stack JS: catching sync and async errors, Promise unhandledrejection, global fallbacks, and exponential-backoff retries. Sun, 06 Sep 2026 00:00:00 GMT language https://laohand.com/guides/dockerfile-security-hardening.html https://laohand.com/guides/dockerfile-security-hardening.html A landing checklist for image maintainers and service containerizers: non-root user, read-only root FS, dropping capabilities, layer hygiene, and image scanning. Sun, 06 Sep 2026 00:00:00 GMT container https://laohand.com/guides/kubernetes-hpa-scaling.html https://laohand.com/guides/kubernetes-hpa-scaling.html For engineers comfortable with Deployments but new to autoscaling: from installing metrics-server, writing an HPA, to load-testing and actually watching replicas scale out. Sun, 06 Sep 2026 00:00:00 GMT container https://laohand.com/guides/docker-compose-troubleshooting.html https://laohand.com/guides/docker-compose-troubleshooting.html Getting to the bottom of ordering, environment variables, port collisions, and service-name DNS inside the compose network, with copyable yaml and debugging commands. Sun, 06 Sep 2026 00:00:00 GMT container https://laohand.com/guides/git-worktree-parallel-dev.html https://laohand.com/guides/git-worktree-parallel-dev.html For devs juggling several branches who fear stash chaos while switching, here is how to keep one clean worktree per task and never stash-swap again. Sun, 06 Sep 2026 00:00:00 GMT vcs https://laohand.com/guides/git-submodule-best-practices.html https://laohand.com/guides/git-submodule-best-practices.html A field guide to when a submodule actually makes sense, how to add, clone, and update it, and the standard escape hatches for empty dirs after clone, branch drift, and nesting. Sun, 06 Sep 2026 00:00:00 GMT vcs https://laohand.com/guides/git-bisect-bug-hunting.html https://laohand.com/guides/git-bisect-bug-hunting.html For anyone tired of hunting commits by gut feel, this is the binary-search way to find the commit that broke something, including making the check scriptable so bisect runs hands-free. Sun, 06 Sep 2026 00:00:00 GMT vcs https://laohand.com/guides/git-merge-conflict-resolution.html https://laohand.com/guides/git-merge-conflict-resolution.html For developers branching daily, this guide reads merge conflict markers end to end with reproducible cases and shows how to handle merge, rebase, and rename conflicts. Sun, 06 Sep 2026 00:00:00 GMT vcs https://laohand.com/guides/http-caching-headers.html https://laohand.com/guides/http-caching-headers.html Misconfigured caching ends one of two ways: users never see updates, or origin traffic explodes. This guide covers the split between freshness and validation caching, the hashed-asset vs HTML strategy divide, plus ready-to-use Nginx config and verification commands. Mon, 31 Aug 2026 00:00:00 GMT web https://laohand.com/guides/yaml-gotchas.html https://laohand.com/guides/yaml-gotchas.html YAML files that "look right but run wrong" usually fail in three places: silently coerced scalars, misplaced indentation, and ambiguous multiline strings. This guide dissects each trap with detection methods and a toolchain. Mon, 31 Aug 2026 00:00:00 GMT config https://laohand.com/guides/bash-safe-scripting.html https://laohand.com/guides/bash-safe-scripting.html A Bash script that "finishes" is not a script that "worked": failed commands do not stop it, empty variables pass silently, and pipes hide upstream crashes. This guide fixes all of them with a copy-ready skeleton (set -euo pipefail + trap + quoting discipline). Mon, 31 Aug 2026 00:00:00 GMT sysops https://laohand.com/guides/vscode-remote-dev.html https://laohand.com/guides/vscode-remote-dev.html A weak laptop, code on an intranet server, GPUs in the cluster — Remote-SSH keeps the UI local while code and terminal run remotely, feeling native. This guide covers setup, passwordless auth, common connection failures and experience tuning. Sun, 30 Aug 2026 00:00:00 GMT devtools https://laohand.com/guides/python-venv-dependencies.html https://laohand.com/guides/python-venv-dependencies.html "Works on my machine" usually means mixed environments. This guide builds a clean flow with the stdlib venv: create, activate, pin and reproduce — plus the three frequent pitfalls: Windows activation, version drift and cross-platform dependencies. Sun, 30 Aug 2026 00:00:00 GMT language https://laohand.com/guides/ssh-passwordless-setup.html https://laohand.com/guides/ssh-passwordless-setup.html Passwordless SSH boils down to one sentence: put the public key into the remote authorized_keys. What blocks you is usually the three hidden gates — file permissions, the home directory, and SELinux. This guide covers the full setup and a step-by-step debugging path. Sun, 30 Aug 2026 00:00:00 GMT web https://laohand.com/guides/k8s-crashloopbackoff-troubleshooting.html https://laohand.com/guides/k8s-crashloopbackoff-troubleshooting.html CrashLoopBackOff is not one error but a state: the container dies on start, and Kubernetes retries with backoff. This guide gives the shortest path — exit code → previous logs → probes → resources → dependencies. Sun, 30 Aug 2026 00:00:00 GMT container https://laohand.com/guides/redis-troubleshooting-playbook.html https://laohand.com/guides/redis-troubleshooting-playbook.html Redis processes commands on a single thread, so one blocking hotspot slows the whole instance. This guide follows the order "memory level → big keys → blocking commands → eviction and persistence", each step with copy-ready commands. Sun, 30 Aug 2026 00:00:00 GMT db https://laohand.com/guides/mysql-slow-query-tuning.html https://laohand.com/guides/mysql-slow-query-tuning.html "The database is slow" usually means a handful of slow SQL statements. This guide offers a repeatable flow: use the slow log to circle the most expensive queries, read the plan with EXPLAIN, decide whether an index pays off, and spot the most common index-defeating patterns. Sun, 30 Aug 2026 00:00:00 GMT db https://laohand.com/guides/linux-cpu-100-locating.html https://laohand.com/guides/linux-cpu-100-locating.html "Restart fixes everything" is the most expensive option when CPU is pegged. This guide gives a reusable path: classify the load, pin the thread, capture what it is executing, then act — with dedicated tools for Java, Python and Go. Sun, 30 Aug 2026 00:00:00 GMT sysops https://laohand.com/guides/linux-disk-full-troubleshooting.html https://laohand.com/guides/linux-disk-full-troubleshooting.html A "No space left on device" error does not mean you should delete files at random. This guide walks through the full path — filesystem water level, directory drill-down, and "deleted but still held" files — plus a safe cleanup order that will not destroy data. Sun, 30 Aug 2026 00:00:00 GMT sysops https://laohand.com/guides/nginx-502-troubleshooting.html https://laohand.com/guides/nginx-502-troubleshooting.html A 502 means Nginx itself is fine but got an invalid response from the upstream (backend/proxy). This guide gives the shortest path: process → config → timeout → resources → logs. Mon, 24 Aug 2026 00:00:00 GMT web https://laohand.com/guides/docker-image-slimming.html https://laohand.com/guides/docker-image-slimming.html Bigger images mean slower pulls, larger attack surface and higher storage cost. This guide gives 5 immediately applicable slimming steps, each with a reusable Dockerfile snippet and a verification command. Mon, 24 Aug 2026 00:00:00 GMT container https://laohand.com/guides/git-accident-recovery.html https://laohand.com/guides/git-accident-recovery.html The scariest moment in daily work is "oh no, I messed up a commit or branch". This guide gives copy-ready recovery commands for real accident scenarios, with clear safety boundaries for each. Mon, 24 Aug 2026 00:00:00 GMT vcs https://laohand.com/plandex.html https://laohand.com/plandex.html Plandex (alias pdx) is a planning-first open-source terminal AI coding agent, for developers who prefer the AI to break a large change into a clear multi-step plan, execute incrementally, and track progress. Unlike modify-directly agents it stresses planning-first and branch-based iteration, suiting big refactors. This sheet covers install/auth, new/load planning, tell execution, and branch iteration. · Sections: Install & Auth, Plan & Load, Execute & Iterate · e.g. curl -sL https://plandex.ai/install.sh | bash, export OPENAI_API_KEY=..., plandex Wed, 26 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/antigravity.html https://laohand.com/antigravity.html Antigravity CLI (command `agy`) is Google terminal AI coding agent, for developers who want Google-ecosystem models plus disciplined planning and permission control. It emphasizes plan-before-execute with transparent /planning and /permissions, and offers subagent management. This sheet covers install, sessions & planning modes, MCP integration, and permission setup. · Sections: Install & Launch, Sessions & Planning, Tools & Integrations · e.g. curl -fsSL https://antigravity.google/cli/install.sh | bash, irm https://antigravity.google/cli/install.ps1 | iex, agy Wed, 26 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/crush.html https://laohand.com/crush.html Crush is the Charmbracelet Rust single-binary terminal AI coding agent, for developers who like lightweight distribution, a single file to run an agent, and a polished TUI. It focuses on stability and observability, offering crush logs diagnostics and a --yolo fast-approve path. This sheet covers install, sessions & modes, and logs/MCP configuration. · Sections: Install & Launch, Sessions & Modes, Configuration · e.g. brew install charmbracelet/tap/crush, npm install -g @charmland/crush, winget install charmbracelet.crush Wed, 26 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/warp.html https://laohand.com/warp.html Warp Agent CLI is the AI coding agent built into the Warp terminal, for developers already on Warp who want slash-command access to the logged-in agent. It is deeply integrated into Warp: /plan for planning, /orchestrate for multi-agent orchestration, and oz agent run to push work to the cloud. This sheet covers core agent commands, MCP integration, and cloud agents. · Sections: Install & Launch, Core Agent Commands, Integrations & Cloud Agents · e.g. brew install --cask warp, sudo dpkg -i warp-terminal_*.deb, warp Wed, 26 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/grok-cli.html https://laohand.com/grok-cli.html Grok CLI is the xAI Grok Build terminal AI coding agent, for developers who want to code, analyze projects, and run scripts with xAI Grok models in the terminal. It authenticates with XAI_API_KEY, offers grok inspect to review context/config, and its -p headless mode plugs into scripts. This sheet covers install, sessions, headless execution, and project analysis. · Sections: Install & Auth, Interactive & Sessions, Headless Mode & Scripts · e.g. curl -fsSL https://x.ai/cli/install.sh | bash, irm https://x.ai/cli/install.ps1 | iex, grok --version Wed, 26 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/kimi-cli.html https://laohand.com/kimi-cli.html Kimi Code CLI is Moonshot AI terminal AI coding agent, wired out of the box to Kimi models, for developers in the Kimi ecosystem who want to edit code and ask questions with Kimi directly in the terminal. It is optimized for Kimi out of the box, removing manual model wiring. This sheet covers install, interactive and -p single instructions, session resume, and /model switching. · Sections: Install & Launch, Interactive & Single Instructions, Sessions & Models · e.g. npm install -g @moonshot-ai/kimi-code, curl -fsSL https://code.kimi.com/kimi-code/install.sh | bash, kimi --version Wed, 26 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/pi.html https://laohand.com/pi.html Pi is the earendil-works multi-model terminal coding agent, for developers who want to switch between several models quickly in the terminal, reference files with @file, and run prompts headlessly in bulk. It is lightweight and script friendly, made for embedding coding/QA tasks in workflows. This sheet covers install/login, interactive and headless modes, session management, and switching models mid-session. · Sections: Install & Auth, Interactive Sessions, Headless Mode & Scripts · e.g. npm install -g @earendil-works/pi-coding-agent, pi, export ANTHROPIC_API_KEY=sk-ant-... Wed, 26 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/kilo-code.html https://laohand.com/kilo-code.html Kilo Code CLI shares its engine with the Kilo Code VS Code/JetBrains extensions, for developers who want the same agent outside the IDE — running one-off tasks (kilo run) while still having a TUI. Being same-engine, it fits scripted/pipeline one-shot code work. This sheet covers install, interactive/one-off tasks, model switching, and MCP. · Sections: Install & Launch, Interactive & One-off Tasks, Models & Integrations · e.g. npm install -g @kilocode/cli, kilo --version, kilo Wed, 26 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/hermes-agent.html https://laohand.com/hermes-agent.html Hermes Agent is Nous Research open-source, model-agnostic terminal AI agent, for developers who want tool-calling on top of any model — decoupling models from underlying tools and centralizing model config, tool declarations, and a message gateway. More flexible than single-vendor agents, it suits self-hosted/multi-model teams. This sheet covers one-line install, customizing with hermes model/tools/config set, and gateway integration. · Sections: Install & Launch, Model & Tool Config, Gateway & Wizard · e.g. curl -fsSL https://raw.githubusercontent.com/NousResearch/hermes-agent/main/scripts/install.sh | bash, pipx install hermes-agent, pip install hermes-agent Wed, 26 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/continue-cli.html https://laohand.com/continue-cli.html Continue CLI (command `cn`) is an open-source terminal coding agent sharing the engine with the Continue VS Code/JetBrains extensions, for developers who want a consistent AI-coding experience across editors and the terminal and prefer keyboard/script-driven work. Being same-engine means context and config from the plugins apply in the terminal too. This sheet covers install, interactive/headless modes, login, and thread resume. · Sections: Install & Auth, Interactive (TUI), Headless (scripts/CI) · e.g. curl -fsSL https://raw.githubusercontent.com/continuedev/continue/main/extensions/cli/scripts/install.sh | bash, cn --version, cn login Sun, 23 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/llamafile.html https://laohand.com/llamafile.html llamafile is Mozilla single-executable approach to running local LLMs, for developers who want zero-friction copy-and-run models — ideal for distribution, offline, and demo use. It packs model weights and llama.cpp into one cross-platform executable with a built-in OpenAI-compatible server. This sheet covers single-file launch, --server, -m GGUF loading, -ngl GPU layers, and --temp sampling. · Sections: Get & Run, OpenAI-compatible Server, Load External Weights · e.g. curl -L <release-url> > llamafile && chmod +x llamafile, ./mistral.llamafile, ./llamafile --help Sun, 23 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/vllm.html https://laohand.com/vllm.html vLLM is a high-throughput LLM inference and serving engine, for production teams that deploy open models behind an OpenAI-compatible API and use tensor parallelism with quantization to maximize GPU throughput. Unlike single-machine tools such as llama.cpp, vLLM focuses on server-grade serving and batching optimizations. This sheet covers install, starting with vllm serve, port/auth configuration, and tensor parallelism. · Sections: Install, OpenAI-compatible Server, Client Calls · e.g. pip install vllm, pip install vllm --upgrade, vllm --version Sun, 23 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/litellm.html https://laohand.com/litellm.html LiteLLM is a unified OpenAI-compatible gateway for 100+ LLMs, for teams that want to reach many providers behind one standard OpenAI surface with unified auth and cost control. One SDK/proxy calls every model instead of writing per-vendor adapters. This sheet covers one-line proxy launch, multi-model routing via --config, and --test connectivity checks. · Sections: Install, Start Proxy (one-liner), Config-driven (prod) · e.g. uv tool install 'litellm[proxy]', pip install "litellm[proxy]", litellm --version Sun, 23 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/amp.html https://laohand.com/amp.html Sourcegraph Amp is Sourcegraph terminal AI coding agent, for developers who need quick one-shot questions or want to push long tasks to run asynchronously in the background instead of blocking the foreground session. It is lightweight and controllable, organizing prompts and background jobs with threads. This sheet covers install/login, one-shot prompts, background execution, and thread management. · Sections: Install & Auth, One-shot Prompts, Thread Management · e.g. npm install -g @sourcegraph/amp, amp --version, amp login Sun, 23 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/amazon-q.html https://laohand.com/amazon-q.html Amazon Q Developer CLI is AWS official terminal AI coding agent, aimed at developers who live in the AWS ecosystem and want the model to understand and edit a local repo while connecting to AWS services/docs. It stands out by deep AWS integration (explaining and acting on AWS resources) and supports both q one-line queries and agent mode. This sheet covers install/login, chat/one-line queries, and agent execution. · Sections: Install & Auth, Chat & Query, Agent Mode · e.g. brew install amazon-q, q --version, q login Sun, 23 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/code-prompts.html https://laohand.com/code-prompts.html Code-generation prompt templates organized by module — requirement/context, constraints, I/O contract, edge/tests, acceptance. Copy a template, fill the variables, and ship. · Sections: Requirement & Context, Constraints & Contract, Edge & Tests · e.g. Task: {do X}. Context: {existing structure/deps}., Relevant code: ```{lang} {code} ```, Target file/func: {path#func}; change only what is needed Sun, 23 Aug 2026 00:00:00 GMT ai-prompt https://laohand.com/image-prompts.html https://laohand.com/image-prompts.html Text-to-image prompt-structure templates organized by module — subject, style, composition, light, negatives, params. Copy a template, fill the variables, and ship. · Sections: Subject & Detail, Style & Artists, Composition & Lens · e.g. Subject: {object/person}, details: {material/expression/action}, Shot: {close-up/full/wide}; {environment} bg, Era/context: {cyberpunk 2099/Tang dynasty} Sun, 23 Aug 2026 00:00:00 GMT ai-prompt https://laohand.com/agent-prompts.html https://laohand.com/agent-prompts.html AI agent system-prompt templates organized by module — goal, tools, guardrails, reflection. Copy a template, fill the variables, and ship. · Sections: Goal & Role, Tool Declaration, Guardrails & Permissions · e.g. You are {role}. Goal: {goal}. Success = {criteria}., Your boundaries: can do {X}; cannot do {Y}., You serve {user/system}; default-prioritize {value}. Sun, 23 Aug 2026 00:00:00 GMT ai-prompt https://laohand.com/rag-prompts.html https://laohand.com/rag-prompts.html RAG prompt templates organized by pattern — answer-from-context, citations, abstain, conflict flags. Copy a template, fill the variables, and ship. · Sections: Answer From Context, Citations & Fusion, Conflict & Uncertainty · e.g. Use only the <context> below; no outside knowledge. Q: {q} <context>{c}</context>, Support each claim with <context> verbatim and cite passage numbers, If <context> is insufficient, say "not enough info" — do not guess Sun, 23 Aug 2026 00:00:00 GMT ai-prompt https://laohand.com/prompt-engineering.html https://laohand.com/prompt-engineering.html General prompt-engineering templates organized by pattern — role, structure, CoT, self-verification. Copy a template, fill the variables, and ship. · Sections: Role Anchoring, Structured Output, Constraints & Few-shot · e.g. You are a senior {domain} expert (10+ yrs); answer professionally but clearly: {q}, As a {role}, complete per {spec}: {task}, Identity={role}; Goal={goal}; Constraints={c}. Start: {input} Sun, 23 Aug 2026 00:00:00 GMT ai-prompt https://laohand.com/github-copilot.html https://laohand.com/github-copilot.html GitHub Copilot CLI brings Copilot to the terminal as a gh extension, for developers who want to quickly explain unfamiliar commands, generate complex shell suggestions, and get AI help instead of memorizing flags. It acts like a command-line translator rather than a full coding agent, focusing on precise explain/suggest help rather than bulk code edits. This sheet covers asking in English/Chinese, alias binding, and configuration. · Sections: Explain Commands, Generate Suggestions, Alias & Config · e.g. gh copilot explain "git rebase -i HEAD~3", gh copilot explain "kubectl get pods", gh copilot explain "awk ..." Fri, 21 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/qwen-code.html https://laohand.com/qwen-code.html Qwen Code is Alibaba Qwen open-source AI coding CLI (Claude Code-like, built on Qwen3-Max / Qwen3-Coder), for developers using Tongyi/Qwen models who want terminal-based AI coding, especially those already on Alibaba Cloud DashScope. Usage resembles Claude Code but with different models and pricing, connecting via DASHSCOPE_API_KEY. This sheet covers launch, print mode, slash commands, and MCP. · Sections: Install & Auth, Launch & Run, Slash Commands · e.g. npm install -g @qwen-code/qwen-code, qwen --version, export DASHSCOPE_API_KEY="sk-..." Fri, 21 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/ollama.html https://laohand.com/ollama.html Ollama is the de-facto runtime for running LLMs locally, for developers and privacy-sensitive teams who want models offline on their own machine plus one-command serving. It is far easier than hand-rolling llama.cpp, with unified model management and an OpenAI-compatible API. This sheet covers pulling/running models, tag management, Modelfile temperature/weight tuning, and serving. · Sections: Run & Chat, Model Management, Modelfile · e.g. ollama run llama3.1, ollama run llama3.1 "summarize in one line", ollama run -m Fri, 21 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/cline.html https://laohand.com/cline.html Cline is one of the most popular VS Code AI coding extensions (formerly Claude Dev, Apache-2.0, multi-provider), for developers who want AI-assisted coding without leaving the editor. It splits planning and execution into Plan/Act phases and injects context via @file/@folder; compared to pure terminal agents the learning curve is lower and visuals are richer. This sheet covers command palette entries, context references, and both modes. · Sections: Command Palette Entries, Context References, Plan & Act Modes · e.g. Cline: Ask, Cline: Explain, Cline: Refactor Fri, 21 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/openhands.html https://laohand.com/openhands.html OpenHands is an open-source autonomous coding agent for developers who want the AI to plan end-to-end and write complete functionality into a repo — even a whole repo. Unlike helpers that confirm every command, it emphasizes autonomous execution with approval/headless modes, suiting batch work (CI, benchmarks, large-scale refactors). This sheet covers launch, task execution, approval modes, headless, and MCP. · Sections: Launch & Task, Resume & Headless, Run Modes (Web/ACP/Cloud) · e.g. openhands, openhands -t "Implement user auth", openhands -f task.txt Fri, 21 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/goose.html https://laohand.com/goose.html Goose is a general-purpose terminal AI agent under the Linux Foundation AAIF (Rust, Apache-2.0), for developers and ops who want one capable agent to manipulate local files, run commands, and connect to 15+ model providers and 70+ MCP extensions. Broader than code-focused agents, it fits handing daily automation and cross-tool workflows to a single agent. This sheet covers interactive sessions, one-shot runs, extension management, and goose doctor diagnostics. · Sections: Session & Run, Configure & Auth, Extensions (MCP) · e.g. goose session, goose session --name feat/login, goose session --resume Fri, 21 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/opencode.html https://laohand.com/opencode.html OpenCode is an open-source Claude Code-style terminal AI coding agent (TUI) for developers who prefer keyboard-driven terminal coding and free provider/model choice. Unlike closed tools it is self-hostable, works with many models, and mounts external tools via MCP. This sheet covers session resume, --fork branching, subagents, and MCP management. · Sections: Launch & Run, CLI Flags, Subcommands · agent / auth · e.g. opencode, opencode "Refactor the auth module", opencode -c Fri, 21 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/notebooklm-prompts.html https://laohand.com/notebooklm-prompts.html Essential NotebookLM prompt templates — source management, inline citations, verification prompts, study/audio generation. Copy a template, fill the variables, and ship. · Sections: Upload & Source Management, Citations & Verification, Study Modes · e.g. Upload PDF / URL / transcript / spreadsheet, Build a master corpus; split large files before upload, Answer only from uploaded sources (boundary) Fri, 21 Aug 2026 00:00:00 GMT ai-prompt https://laohand.com/perplexity-prompts.html https://laohand.com/perplexity-prompts.html Essential Perplexity prompt templates — questioning style, Focus modes, date constraints, chained follow-ups. Copy a template, fill the variables, and ship. · Sections: Questioning Style, Focus Modes, Date & Source Constraints · e.g. Write a full question, not keyword soup, State goal and constraints: audience/depth/use, Scope it: region/industry/time Fri, 21 Aug 2026 00:00:00 GMT ai-prompt https://laohand.com/kling-prompts.html https://laohand.com/kling-prompts.html Essential Kling AI (Kling) video prompt templates — camera moves, six-segment structure, API params. Copy a template, fill the variables, and ship. · Sections: Camera Moves, Camera Rules, Six-Segment Structure · e.g. push-in / pull-out, pan (left-right) / tilt (up-down), dolly (fore-aft) / orbit (around subject) Fri, 21 Aug 2026 00:00:00 GMT ai-prompt https://laohand.com/stable-diffusion-prompts.html https://laohand.com/stable-diffusion-prompts.html Essential Stable Diffusion / SDXL prompt templates — six-segment structure, weight syntax, LoRA, sampling params. Copy a template, fill the variables, and ship. · Sections: Six-Segment Structure, Weight Syntax, Negative Prompts · e.g. [Subject] + [Action/Pose], [Environment], [Lighting/Mood] Fri, 21 Aug 2026 00:00:00 GMT ai-prompt https://laohand.com/gemini-prompts.html https://laohand.com/gemini-prompts.html Essential Gemini prompt templates — structured delimiters, long-context anchoring, multimodal input, model selection. Copy a template, fill the variables, and ship. · Sections: Structured Delimiters, Long-Context Anchoring, Thinking & Date / Grounding · e.g. Wrap sections in XML tags: <context>...</context><task>...</task>, Use Markdown headings (## Background / ## Task) as separators, Put role and constraints in system instruction or at the start of user Fri, 21 Aug 2026 00:00:00 GMT ai-prompt https://laohand.com/deepseek-prompts.html https://laohand.com/deepseek-prompts.html Essential DeepSeek prompt templates organized by model — R1 reasoning rules, V3 chat tricks, codegen, structured output. Copy a template, fill the variables, and ship. · Sections: R1 Reasoning Rules (deepseek-reasoner), V3 Chat Rules (deepseek-chat), Code Generation · e.g. No system prompt — put all instructions in the user message, Do not use few-shot examples; let the model reason alone, Set temperature to 0.6 Fri, 21 Aug 2026 00:00:00 GMT ai-prompt https://laohand.com/aider.html https://laohand.com/aider.html Aider is the open-source Apache 2.0 terminal AI pair programmer for developers who want a model to edit local files and auto git-commit, with 100+ model support and no vendor lock-in. Its signature is an automatic commit per change, forming a safe loop with --test-cmd/--lint-cmd where a bad edit is one /undo away. This sheet covers file context, chat-mode switching, and architect mode. · Sections: Install & Start, Model & Reasoning, Files & Context · e.g. pip install aider-chat, aider, aider src/main.py tests/test_main.py Wed, 05 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/cursor.html https://laohand.com/cursor.html Cursor is the VS Code-based AI editor; its CLI and cursor-agent target developers who open projects quickly, manage windows/extensions, and want editor + AI capability inside scripts. Unlike a plain editor CLI, Cursor adds in-editor AI coding and the headless-callable cursor-agent. This sheet covers opening/comparing files from the terminal, agent automation, and git editor integration. · Sections: Open Files & Folders, Window Management, Diff & Merge · e.g. cursor ., cursor /path/to/file.ts, cursor /path/to/file.ts:42 Wed, 05 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/gemini-cli.html https://laohand.com/gemini-cli.html Gemini CLI is Google open-source terminal AI agent (Apache 2.0) for developers who need very long context and want the model to edit code autonomously against their own models; its 2M-token window fits whole-repository refactoring and analysis. Long context, forkable self-hosting, and GEMINI.md project memory set it apart. This sheet covers install/auth, headless automation (-p -o json), and MCP/extensions. · Sections: Install & Auth, Run Modes, Global Flags · e.g. npm install -g @google/gemini-cli, gemini --version, gemini Wed, 05 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/codex-cli.html https://laohand.com/codex-cli.html Codex CLI is OpenAI official open-source terminal coding agent (Rust) for developers driving GPT-family models to edit code, run tests, and manage approvals directly in a repo — and for CI engineers adopting AI codegen/review. Unlike cloud chat it adds fine-grained sandbox (read-only/workspace-write/full-access) and approval policies, plus headless codex exec --json for pipelines. This sheet covers install/login, non-interactive execution, and the sandbox trade-offs. · Sections: Install & Auth, Interactive Mode, Non-interactive (codex exec) · e.g. npm install -g @openai/codex, brew install --cask codex, codex --version Wed, 05 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/claude-code.html https://laohand.com/claude-code.html Claude Code targets developers who want the model to read, edit, and run commands inside a repo from the terminal, plus automation engineers wiring it into CI. As Anthropic official agentic coding tool it differs from chat-style assistants, and drives pipelines headlessly via -p + --output-format json or iterative multi-turn REPL sessions. This sheet surfaces the key commands for install/auth, session resume, permission modes, and MCP extensibility so you can start on real projects immediately. · Sections: Install & Auth, Launch & Run, CLI Flags · e.g. npm install -g @anthropic-ai/claude-code, claude --version, npm update -g @anthropic-ai/claude-code Wed, 05 Aug 2026 00:00:00 GMT ai-cli https://laohand.com/http-methods.html https://laohand.com/http-methods.html The hard part of API design is rarely syntax — it's deciding whether this endpoint is PUT or PATCH, and whether retrying is safe. Grouped by method semantics, idempotency, safe attributes and status-code pairing, this table explains why POST is non-idempotent and why PUT replaces whole resources while PATCH updates a subset. Use it to pick verbs from business intent so retries and concurrent calls behave predictably. · Sections: Core Methods, Idempotency & Safety, Status Pairing · e.g. GET, POST, PUT Sun, 02 Aug 2026 00:00:00 GMT reference https://laohand.com/dockerignore.html https://laohand.com/dockerignore.html If you skip .dockerignore, docker build . packs node_modules and .git into the build context, slowing builds and bloating images. This reference covers 5 groups: basic syntax, glob patterns, common ignores, differences from .gitignore, and slimming tips. After writing a template, verify the context size with docker build, and remember a ! negation only re-includes items already ignored. After reading you can ship a safe, lean .dockerignore for your project. · Sections: Basic Syntax, Glob Patterns, Common Ignores · e.g. node_modules, *.log, tmp/ Sun, 02 Aug 2026 00:00:00 GMT config https://laohand.com/env.html https://laohand.com/env.html Almost every Node/Python/frontend project writes a .env, yet the most common traps are spaces around the equals sign, a # inside a value treated as a comment, and secrets accidentally committed to the repo. This reference covers 5 groups: variable definition, reading in Shell/Node/Python, dotenv loader usage, multi-environment file layout (.env/.env.local/.env.production), and a set of security-pitfall reminders. Sanity-check the format after writing and confirm no secrets were committed before deploying. After reading you can organize environment variables cleanly and avoid the most common leakage issues. · Sections: Definition, Reading, dotenv Usage · e.g. KEY=value, KEY="value with space", KEY='literal $NOT_EXPANDED' Sun, 02 Aug 2026 00:00:00 GMT config https://laohand.com/regex.html https://laohand.com/regex.html The usual regex pain point is not remembering metacharacters, but whether to reach for ? or *, whether to use lookahead or lookbehind, and whether your pattern is greedy or lazy. This reference groups character classes, quantifiers, capture groups and these assertions separately, each with an explanation and a real-world template. When validating a form or filtering logs, find the group that matches your target, then adjust the boundaries against the template. · Sections: Character Classes, Anchors, Quantifiers · e.g. [abc], [^abc], [a-z] Sun, 02 Aug 2026 00:00:00 GMT regex https://laohand.com/sql.html https://laohand.com/sql.html For developers who write SQL that is both business-correct and fast. The traps are usually not in the syntax itself but in NULL propagation, filtering after GROUP BY requiring HAVING, and where window functions stop overlapping plain aggregation. By the end you can write correct queries with grouping and filtering clauses, use window functions for row numbers and in-group ranking instead of self-joins, dodge NULL comparisons and aggregation pitfalls, and wrap multi-statement work in transactions for atomicity. · Sections: Basic Query, Filtering & Logic, Aggregation & Grouping · e.g. SELECT * FROM users, SELECT name, age FROM users, SELECT * FROM users WHERE age > 18 Sun, 02 Aug 2026 00:00:00 GMT db https://laohand.com/web-fetch.html https://laohand.com/web-fetch.html For engineers who call APIs, download files, and debug HTTP purely from the shell. Though often paired, curl and wget have different roles: curl is an HTTP client that suits API calls with methods/headers/cookies, while wget leans toward file fetching with clean resume and recursive mirroring. By the end you can pick the right tool per task, resume large downloads with wget -c, trace API issues with curl -v/-w, and handle proxies and auth. · Sections: Basic Requests, HTTP Method, Headers & Cookies · e.g. curl https://api.test, curl -O https://x/file.zip, curl -o out.html https://x Sun, 02 Aug 2026 00:00:00 GMT web https://laohand.com/gitignore.html https://laohand.com/gitignore.html Committing node_modules or .env by accident is a trap nearly every repo hits once. This .gitignore reference organizes 5 groups — basic matching syntax, wildcards and comments, directories vs files, global ignore and effect commands, plus common language templates. When unsure whether a rule matches, verify with git check-ignore -v; for already-tracked files, un-track with git rm --cached first. After reading you can write ignore rules that stay safe without leaking files. · Sections: Basic Syntax, Wildcards & Comments, Dirs & Files · e.g. *.log, build/, /dist Sun, 02 Aug 2026 00:00:00 GMT vcs https://laohand.com/slack-shortcuts.html https://laohand.com/slack-shortcuts.html Slack users drowning in messages should first learn Cmd/Ctrl+K to jump to any channel or DM, Cmd/Ctrl+Shift+M to see only mentions of you, and Shift+Esc to mark everything read — three bindings that save a lot of clicking. This reference organizes 5 groups covering message editing, channel browsing, conversation navigation, global search and formatting, with macOS and Windows side by side. After reading you will communicate and track messages noticeably faster. · Sections: Messages, Channels, Navigation · e.g. Enter / Enter, Shift+Enter / Shift+Enter, ↑ / ↑ Fri, 31 Jul 2026 00:00:00 GMT shortcuts https://laohand.com/chrome-shortcuts.html https://laohand.com/chrome-shortcuts.html Front-end developers who juggle a dozen tabs should start with Cmd/Ctrl+T for a new tab and Cmd/Ctrl+Shift+T to restore a misclosed one; to tweak styles use Cmd/Ctrl+Option+I for DevTools and Cmd/Ctrl+Shift+C to pick an element. This reference organizes 6 groups with macOS and Windows side by side. After reading you will click less and get through daily browsing and front-end debugging faster. · Sections: Tabs, Windows, Browsing · e.g. Cmd+T / Ctrl+T, Cmd+W / Ctrl+W, Cmd+Shift+T / Ctrl+Shift+T Fri, 31 Jul 2026 00:00:00 GMT shortcuts https://laohand.com/windows-shortcuts.html https://laohand.com/windows-shortcuts.html Heavy Windows users who switch windows often and snap across multiple monitors should learn three groups first: Win+Arrow to snap, Alt+Tab to switch, and Ctrl+Shift+Esc to open Task Manager directly; File Explorer and Command Line bindings can wait until you are comfortable. This reference organizes 6 groups so you can quickly locate a binding by category. After reading, your window-management and screenshot efficiency will visibly improve. · Sections: General, File Explorer, Screenshots · e.g. Win, Win+S, Win+I Fri, 31 Jul 2026 00:00:00 GMT shortcuts https://laohand.com/macos-shortcuts.html https://laohand.com/macos-shortcuts.html If you just switched to macOS or want to gradually move off the mouse, start with these six groups: app switching (Cmd+Tab), screenshots (Cmd+Shift+4), window management (Cmd+M/H) and text editing. You do not need to memorize them all at once — learn the screenshot and window-management ones first for the most visible daily time saved, then layer in Finder and system shortcuts as muscle memory forms. · Sections: General, Finder, Screenshots · e.g. Cmd+Space, Cmd+Tab, Cmd+Shift+Tab Fri, 31 Jul 2026 00:00:00 GMT shortcuts https://laohand.com/midjourney-prompts.html https://laohand.com/midjourney-prompts.html Midjourney AI art prompts and parameters organized by Basics, Style, Composition, Lighting, Negative & Weights, and Advanced. Combine parameters and generate. · Sections: Basic Parameters (--ar/--v/--q/--n), Style Keywords (photorealistic/anime/oil painting), Composition & Camera (close-up/wide angle/aerial) · e.g. --ar 16:9, --ar 9:16, --ar 1:1 Fri, 31 Jul 2026 00:00:00 GMT ai-prompt https://laohand.com/claude-prompts.html https://laohand.com/claude-prompts.html Claude prompt reference built around its 200K long context and Constitutional AI: how to feed whole long documents without losing global context, set role-play boundaries, keep multi-turn consistency, and request structured output — each with an adaptable template skeleton for your input. · Sections: Long Document Processing (200K Context), Code Generation & Analysis, Role-play & System Prompts · e.g. Read the following long document and answer the question. Document: {long doc} Question: {question}, Compare the following two long documents across structure, content, and viewpoints: Doc A: {doc A} Doc B: {doc B}, Distill the following 50-page meeting notes into an executive summary with: key decisions, action items, owners, deadlines: {notes} Fri, 31 Jul 2026 00:00:00 GMT ai-prompt https://laohand.com/chatgpt-prompts.html https://laohand.com/chatgpt-prompts.html Essential ChatGPT prompt templates organized by Role Setting, Structured Output, Code, Text Processing, Few-shot, and Chain of Thought. Copy a template, fill the variables, and ship. · Sections: Role Setting (System Role), Structured Output (JSON/Table/Markdown), Code (Generate/Review/Explain/Refactor) · e.g. You are a senior {domain} expert with 10+ years of experience. Answer the following in a professional yet accessible way: {question}, As a {role}, complete the following task strictly following {standard/spec}: {task}, Your identity is {role}, your goal is {goal}, your constraints are {constraints}. Begin: {input} Fri, 31 Jul 2026 00:00:00 GMT ai-prompt https://laohand.com/datetime.html https://laohand.com/datetime.html Date bugs are usually timezone bugs — a timestamp that looks right locally is off by 8 hours elsewhere. Organized by strftime tokens, ISO 8601, timezones/offsets, per-language methods and timestamp conversion, this table lets you map a token to its output and avoid the classic UTC vs local pitfall. Use it when formatting logs, building API timestamps, or parsing ISO strings. After reading you pick a format that round-trips consistently across servers and clients. · Sections: strftime Format Specifiers, ISO 8601 Standard, Timezone & Offset · e.g. %Y, %y, %m Tue, 21 Jul 2026 00:00:00 GMT reference https://laohand.com/cidr.html https://laohand.com/cidr.html IP-address math is where admins make their costliest slips — a /23 instead of /24 halves your host count silently. This reference maps prefixes to masks and host counts, lists private and special-purpose ranges, and shows how to split/merge subnets. Use it to size a VPC, compose firewall allowlists, and sanity-check a natting table. After reading you compute hosts and ranges without a binary calculator. · Sections: CIDR Notation Basics, Subnet Mask Reference, Common Subnet Sizes · e.g. 192.168.1.0/24, IP/前缀, /24 Tue, 21 Jul 2026 00:00:00 GMT reference https://laohand.com/rest-api.html https://laohand.com/rest-api.html Inconsistent endpoint naming is what turns a healthy API into a guessing game for every frontend engineer. Organized by URL design, methods, status codes, headers/formats, auth and practices, each entry is a convention you can apply directly. Use it to sketch a resource model, choose /users/{id} over /getUser, and align on error framing. After reading you produce an API whose shape your frontend bets on safely. · Sections: URL Design Spec, HTTP Methods, Common Status Codes · e.g. /api/v1/users, /api/v1/users/123, /api/v1/users/123/orders Tue, 21 Jul 2026 00:00:00 GMT reference https://laohand.com/semver.html https://laohand.com/semver.html A careless constraint like ^ or ~ silently decides whether your deploy upgrades dependencies or breaks the build. This reference covers MAJOR.MINOR.PATCH structure, prerelease tags, comparison operators, and the npm ranges you actually write (^ ~ >= < * and advanced combos). Use it to write a package.json that upgrades exactly what you want, and to tell why npm picked version X. After reading you read and write version ranges with intent. · Sections: Version Number Structure, Pre-release & Build Metadata, Version Comparison Operators · e.g. MAJOR.MINOR.PATCH, 1.2.3, MAJOR：不兼容的 API 变更 Tue, 21 Jul 2026 00:00:00 GMT reference https://laohand.com/iso-639-1.html https://laohand.com/iso-639-1.html Localization breaks silently when the language you detect doesn't match the one you ship. Grouped by region, each two-letter code pairs its English and native name so you pick without confusing zh/zh-CN or pt/pt-BR. Use it to set the lang attribute, build Accept-Language negotiation, and store a canonical locale key. After reading you assign locale codes that browsers and backends agree on. · Sections: Asian Languages, European Languages, Middle East & African Languages · e.g. zh, zh-CN, zh-TW Tue, 21 Jul 2026 00:00:00 GMT reference https://laohand.com/aspect-ratio.html https://laohand.com/aspect-ratio.html Designing responsively means designing for a range of viewports, not just your own monitor. Grouped by phone, tablet, laptop, monitor and TV, each device lists its physical and CSS pixels where relevant and its aspect ratio. Use it to choose breakpoints, produce video at the right ratio, and talk to stakeholders about "which screens it must work on". After reading you can justify breakpoint decisions against real devices. · Sections: Phone Resolutions, Tablet Resolutions, Laptop Resolutions · e.g. 320 × 480, 640 × 960, 750 × 1334 Tue, 21 Jul 2026 00:00:00 GMT reference https://laohand.com/emoji-unicode.html https://laohand.com/emoji-unicode.html Emoji look fine on your screen until they break a MySQL column or get mangled in a JSON API. Organized by category, each emoji shows its codepoint and tips on surrogate pairs, ZWJ sequences and UTF-8 storage. Use it to size TEXT columns correctly, reason about why 👨‍👩‍👧 isn't a single codepoint, and handle emoji server-side without corruption. After reading you store and transmit emoji safely. · Sections: Smileys & Emotion, Gestures, Hearts · e.g. 😀 U+1F600, 😂 U+1F602, 😊 U+1F60A Tue, 21 Jul 2026 00:00:00 GMT reference https://laohand.com/html-char-entities.html https://laohand.com/html-char-entities.html Unescaped &, <, > in dynamic HTML is how pages break and how XSS sneaks in. This table lists the entities you actually meet — reserved chars, symbols, arrows, math and Greek letters — each as both a named entity and the &#xNN; numeric form. Use it to escape output, fix mojibake, and know why & alone becomes &amp;. After reading you escape input confidently and render any symbol without hunting byte codes. · Sections: Basic Characters, Common Symbols, Currency Symbols · e.g. &amp; 或 &#38;, &lt; 或 &#60;, &gt; 或 &#62; Tue, 21 Jul 2026 00:00:00 GMT reference https://laohand.com/mime-types.html https://laohand.com/mime-types.html A wrong Content-Type is often the invisible cause of broken downloads, garbled pages and rejected uploads. Organized by file category, each media type maps to extensions, the correct Content-Type string and charset notes. Use it to configure Nginx mime.types, set response Content-Type in server code, and validate what a browser infers from the header. After reading you know why .wasm or .woff2 serves wrong and how to fix it. · Sections: Text Types, Image Types, Audio/Video Types · e.g. text/html, text/css, text/javascript Tue, 21 Jul 2026 00:00:00 GMT reference https://laohand.com/ascii-code.html https://laohand.com/ascii-code.html Protocol and encoding bugs usually boil down to "which byte is which char". This table lists ASCII 0–127 split into control and printable characters, each with decimal, hex, octal and the HTML entity, plus Latin-1 extension notes and per-language conversion tips. Use it to decode raw bytes, format terminal-control escapes, and understand what \n \r \t \0 really are. After reading you can translate between representations by hand. · Sections: Control Characters (0-31, 127), Printable Characters (32-126), Common Control Characters · e.g. 0 (0x00), 3 (0x03), 4 (0x04) Tue, 21 Jul 2026 00:00:00 GMT reference https://laohand.com/latex.html https://laohand.com/latex.html LaTeX rewards sticking to a few reliable snippets and punishes improvising at the last minute. Grouped by document structure, text formatting, math, lists, tables and references, each command shows its purpose and common companion packages. Use it to scaffold a paper skeleton, typeset math correctly, and wire up citations without re-opening the boring user guide. After reading you can draft an article that compiles on the first pass. · Sections: Document Structure, Text Formats, Math Formulas · e.g. \documentclass{article}, \usepackage[utf8]{inputenc}, \usepackage{amsmath} Tue, 21 Jul 2026 00:00:00 GMT latex https://laohand.com/markdown.html https://laohand.com/markdown.html Markdown parsing differs across platforms — GitHub, GitLab, VitePress and others each emphasize different subsets. This reference gathers the widely-supported basics plus each platform's GFM extensions, organized by feature (headings, lists, tables, code blocks, …), so you produce docs that render correctly everywhere and know which syntax is not portable. After reading you pick the safest construct instead of discovering breakage after publishing. · Sections: Heading, Text Style, List · e.g. # H1, ## H2, ### H3 Tue, 21 Jul 2026 00:00:00 GMT reference https://laohand.com/http-status-codes.html https://laohand.com/http-status-codes.html A status code usually tells you where to look next instead of where to blame. Grouped by 1xx–5xx, each entry gives the meaning, typical cause and a fix hint, covering both REST responses returned to clients and edge-level errors such as Nginx forwarding and rate limiting. Use it to read logs, align client–server contracts, and tell 401/403 or 302/307 apart for real environments. · Sections: 1xx Informational, 2xx Success, 3xx Redirection · e.g. 100 Continue, 101 Switching Protocols, 200 OK Tue, 21 Jul 2026 00:00:00 GMT reference https://laohand.com/ini.html https://laohand.com/ini.html INI is simple, but parsers differ: the comment character, quote handling, nesting support and variable interpolation all vary by implementation. This reference organizes 8 groups of basic syntax and data types, plus four real-world scenarios — Windows, php.ini, Git config and Python configparser — and a dedicated parsing-caveats group on cross-parser differences. After reading you can judge quickly whether a given INI block is safe in the target parser and avoid common traps like BOM, duplicate keys and comment-character issues. · Sections: Basic Syntax, Data Types, Common Applications · e.g. ; this is a comment, # this is also a comment, [section] Tue, 21 Jul 2026 00:00:00 GMT ini https://laohand.com/toml.html https://laohand.com/toml.html Tools like Cargo, Hugo and Greenlet configure with TOML, whose explicit [table] blocks and key = value syntax make it more readable than JSON and support comments. This reference groups 6 sections: basic types, date-time, four string flavors, arrays and tables, arrays of tables, plus a ready-to-adapt Cargo.toml example. Mirror the structure while writing a dependency table or nested section, and look up string escaping or date-time offsets as needed to avoid common type and indentation ambiguity. After reading you can maintain Cargo.toml and similar TOML config on your own. · Sections: Basic Types, Date & Time, Strings · e.g. # this is a comment, key = "value", key = 'value' Tue, 21 Jul 2026 00:00:00 GMT toml https://laohand.com/json.html https://laohand.com/json.html In frontend-backend integration, JSON is the default format for API responses and one of the easiest to break with a trailing comma or an unquoted key. This reference covers 6 high-frequency groups — data types, objects, arrays, nesting, common API response patterns, and validation/formatting commands (JSON.parse, jq). It helps you write well-formed data from a template and gives you a checklist for debugging plus jq for quick validation. After reading you can assemble valid JSON and verify it with tooling quickly. · Sections: Data Types, Object, Array · e.g. "string", 123 / -456 / 3.14, true / false Tue, 21 Jul 2026 00:00:00 GMT json https://laohand.com/yaml.html https://laohand.com/yaml.html Across Docker Compose, Kubernetes and GitHub Actions, the most common mistakes are wrong indentation, a missing space after the colon, and unquoted special characters. This reference arranges the 8 most-used syntax groups (basics, data types, lists and dicts, multiline strings, anchors and aliases, type tags) by purpose: mirror the scaffolding when writing config, and debug indentation or quoting section by section when an error appears. It also notes where YAML differs from JSON — single quotes do not escape, comments are allowed, and anchors cut repetition. After reading you can write clean, maintainable config files on your own. · Sections: Basic Syntax, Data Types, List / Array · e.g. key: value, # comment, --- Tue, 21 Jul 2026 00:00:00 GMT yaml https://laohand.com/vite.html https://laohand.com/vite.html Vite trades dev-server startup for a near-instant experience via native ESM and on-demand compilation, and its config reads differently from Webpack. This reference covers scaffolding, the dev server, production build, environment variables, plugins, proxy and SSR builds, and calls out where it diverges from legacy bundling. Use it when starting a project, migrating an older Webpack setup, or when a config you set "just doesn't apply". After reading you can take a project from scaffolding to a production build, and know exactly where to edit for dev vs build. · Sections: Project Creation & Init, Dev Server, Production Build · e.g. npm create vite@latest, npm create vite@latest my-app -- --template react-ts, npm create vite@latest my-app -- --template vanilla-ts Tue, 21 Jul 2026 00:00:00 GMT devtools https://laohand.com/jest.html https://laohand.com/jest.html Tests only earn their keep when a failure tells you precisely what broke. This reference covers describe/it grouping, matchers beyond toBe, async and promise testing, jest.fn/jest.mock module mocking, snapshot testing, and coverage output. It emphasizes the matchers and mock strategies that pinpoint broken behavior instead of vague red. For teams adding real unit coverage to JS/TS code. After reading you write focused assertions and mock the exact seams you intend to. · Sections: Basic Tests, Matchers, Async Tests · e.g. test("desc", () => { expect(1 + 2).toBe(3) }), it("desc", fn), describe("module", () => { it(...) }) Tue, 21 Jul 2026 00:00:00 GMT node https://laohand.com/webpack.html https://laohand.com/webpack.html Webpack’s power is real and its config is where that power lives or hides. This reference covers entry/output, Loaders for each asset type, Plugins, dev-server/HMR, code splitting and optimizations, plus mode/environment. Use it when a new asset type won't load, HMR dies, or a bundle is inexplicably huge. Rather than echo boilerplate, it points to the flag or plugin that addresses the failure. After reading you configure and tune a build without reading the full Webpack docs. · Sections: Entry & Output, Loaders, Plugins · e.g. entry: "./src/index.js", entry: { app: "./src/app.js", vendor: "./src/vendor.js" }, output.filename: "[name].[contenthash].js" Tue, 21 Jul 2026 00:00:00 GMT node https://laohand.com/npm.html https://laohand.com/npm.html A Node project is only as reproducible as your dependency commands. This reference runs the whole lifecycle: init/scaffold, install/update/remove, version ranges and package-lock, npm scripts and npx, npm ls/audit/outdated for health, publishing, and config/cache handles. Compare to a bare command list, it also flags lockfile and audit subtleties that bite teams. Use it when CI fails on dependency resolution or a package won't install at the expected version. After reading you operate dependencies and debug install issues with intent. · Sections: Project Init, Install & Uninstall, Version Management · e.g. npm init -y, npm init, npm init <initializer> [args] Tue, 21 Jul 2026 00:00:00 GMT node https://laohand.com/gitlab.html https://laohand.com/gitlab.html GitLab’s keystrokes differ from GitHub’s in details, and the review flow is where they save the most time. This reference covers global navigation, repo/file search, Issue/MR shortcuts, and Merge-Request review and commenting. Use it when your team standardizes on GitLab CE/EE and you want keyboard-first reviewing and MR triage. After reading you navigate projects, files and MR threads as fast as you click, but with less mousing around. · Sections: Global Navigation, Repository Browsing, Code Browsing · e.g. G then D, G then A, G then M Tue, 21 Jul 2026 00:00:00 GMT devtools https://laohand.com/github.html https://laohand.com/github.html Daily GitHub work — reviewing PRs, hunting files, leaving comments — is full of small repeated clicks. This reference covers global navigation (s and /), repo and file search, code search, Issue/PR hotkeys, review commenting, and Markdown editing. The big wins are keyboard-opened search and quick PR-review commenting. For maintainers and reviewers who spend hours in the browser rather than the terminal. After reading you review, search and comment faster than the mouse allows. · Sections: Global Navigation, Repository Browsing, Code Browsing · e.g. G then N, G then I, G then P Tue, 21 Jul 2026 00:00:00 GMT devtools https://laohand.com/android-studio.html https://laohand.com/android-studio.html Android work is build-loop heavy, and Android Studio’s shortcuts condense that loop. This reference covers Kotlin/Java generation and navigation, the layout editor, Gradle sync, emulator controls, run/debug, and Logcat/Profiler access. The high-yield ones are navigation to implementation, quick build/run, and jumping from an AndroidX call to source. For anyone iterating on screens and APIs all day. After reading you keep the build-test-debug cycle moving mostly with the keyboard. · Sections: Kotlin/Java Development, Layout Editor, Gradle Build · e.g. Cmd + N, Cmd + Option + T, Cmd + Option + M Tue, 21 Jul 2026 00:00:00 GMT devtools https://laohand.com/phpstorm.html https://laohand.com/phpstorm.html PhpStorm’s edge over a plain editor is framework awareness — it knows Laravel/Symfony routes, models and containers. This reference groups PHP generation, framework jump, database, debug/run and quality shortcuts on the JetBrains keymap. Use the framework-navigation keys to hop between a route, controller and blade/twig template without grepping. For PHP work where navigating an unfamiliar codebase is the daily cost. After reading you refactor and jump through a PHP app without breaking stride. · Sections: PHP-specific, Laravel-specific, Database Tools · e.g. Cmd + N, Cmd + Option + T, Cmd + Option + M Tue, 21 Jul 2026 00:00:00 GMT devtools https://laohand.com/webstorm.html https://laohand.com/webstorm.html WebStorm brings JetBrains-grade tooling to JavaScript, and the payoff multiplies once you use its shortcuts. This reference covers editing and reformatting, completion/generation, navigation, refactoring, run/debug, Git and layout, all on the JetBrains keymap. It highlights the keys that matter for JS/TS work — smart completion, extract-to-const, git history — where the IDE genuinely beats editor-plus-CLI. After reading you jump between files, refactor and inspect git state without mousing over toolbar buttons. · Sections: Basic Editing, Completion & Generation, Navigation & Search · e.g. Cmd + D, Cmd + Y, Cmd + Shift + Enter Tue, 21 Jul 2026 00:00:00 GMT devtools https://laohand.com/sublime-text.html https://laohand.com/sublime-text.html Sublime stays beloved because it pairs a tiny footprint with real editing muscle. This reference covers basic editing and folding, the multi-cursor/bulk-edit power you can't get in many heavier editors, quick navigation, search, split layouts, and snippets. It is aimed at people editing large text or quick patches without loading a full IDE. After reading you select, fold and multi-edit pages faster than the mouse allows. · Sections: Basic Editing, Multi-cursor Editing, Navigation & Selection · e.g. Cmd + D, Cmd + Shift + D, Cmd + Shift + K Tue, 21 Jul 2026 00:00:00 GMT devtools https://laohand.com/intellij-idea.html https://laohand.com/intellij-idea.html IntelliJ is powerful enough to be slow to learn; the shortcuts are the unlock. This reference groups navigation, editing/refactoring, generation/completion, run/debug stepping, VCS and layout. It flags high-yield keys like Search Everything, Generate, and Rename across the hierarchy, plus the debugger stepping set. For Java/Kotlin work where jumping between related classes and runtime state is constant. After reading you navigate, refactor and debug without breaking to the mouse. · Sections: Code Navigation, Editing & Refactoring, Code Completion · e.g. Cmd+O, Cmd+Shift+O, Cmd+Alt+L Tue, 21 Jul 2026 00:00:00 GMT intellij-idea https://laohand.com/figma.html https://laohand.com/figma.html Clicking toolbar buttons in Figma is how a 5-minute layout becomes a 40-minute slog. This reference covers tool switching, frames, layer management and auto-layout, alignment, components/styles and exports. Unlike a feature tour, it lists the exact keys to flip frames, group layers, apply auto-layout and swap between tools. After reading you assemble screens and keep layers tidy mostly from the keyboard, which matters most in handoff-heavy workflows. · Sections: Tool Switching, Layer Operations, Align & Distribute · e.g. V, F, R Tue, 21 Jul 2026 00:00:00 GMT figma https://laohand.com/chrome-devtools.html https://laohand.com/chrome-devtools.html Console.log poking is a poor substitute for stepping through a live page. This reference covers Elements and DOM breakpoints, console tricks, Network waterfall and request replay, Performance flame charts, and Application storage. Use it when a page works on your laptop but misbehaves in production — isolate a layout bug, find a slow request, or trace a storage leak. After reading you inspect, measure and fix frontend problems from inside the browser instead of guessing. · Sections: Shortcuts, Console Commands, Elements Debugging · e.g. F12 or Cmd+Option+I, F12 or Ctrl+Shift+I, Cmd+Option+J Tue, 21 Jul 2026 00:00:00 GMT chrome-devtools https://laohand.com/postman.html https://laohand.com/postman.html A single curl proves nothing about auth edge cases or response shapes across environments. Postman turns requests into an environment-aware, scriptable workflow. This reference covers building requests, environment and global variables, test assertions with pm.test, pre-request scripts and dynamic data, plus running whole collections and spinning up Mock servers. Use it when you need repeatable tests for many endpoints, not one-off probes. After reading you automate assertions and re-run suites across dev/staging/prod. · Sections: Request Building, Environment Variables, Test Scripts · e.g. GET {{base_url}}/api/users, POST {{base_url}}/api/users, PUT {{base_url}}/api/users/1 Tue, 21 Jul 2026 00:00:00 GMT postman https://laohand.com/mitmproxy.html https://laohand.com/mitmproxy.html Browser DevTools only sees what your own browser sent; to see other apps' HTTPS traffic you need a MITM proxy. This reference covers mitmproxy/mitmdump/mitmweb modes and ports, filter expressions, flow interception/editing, addon scripts, and the CA-cert install that decrypts HTTPS. Use it when debugging a mobile app, an old client, or a scheduled job that doesn't go through the browser. After reading you can capture, filter and even rewrite live API calls. · Sections: Startup & Modes, Filter Expressions, Interactive Operations · e.g. mitmproxy, mitmweb, mitmdump Tue, 21 Jul 2026 00:00:00 GMT mitmproxy https://laohand.com/xpath.html https://laohand.com/xpath.html Regex is the wrong tool for pulling nodes out of XML/HTML — XPath was built for it. This reference covers node paths, predicate filters, axis navigation, string/functions and wildcards, with the scraping cases you actually meet. Use it when scraping a page, querying an XML config or asserting in tests, instead of writing fragile regex that breaks on whitespace. After reading you write a selector that targets exactly the node you want, including positions and attributes. · Sections: Basic Paths, Predicate Filtering, Axes · e.g. /, //, . Tue, 21 Jul 2026 00:00:00 GMT xpath https://laohand.com/homebrew.html https://laohand.com/homebrew.html A fresh Mac loses hours to $PATH and dependency mess unless you install through Homebrew. This reference covers installing/updating/removing formulas, Cask GUI apps, brew services for background daemons, mirror switches for mainland use and troubleshooting broken bottles. Unlike a package list, it tells you which flag installs from HEAD vs a bottle, and how to diagnose a brew doctor complaint. After reading you can bootstrap and repair a Mac toolchain mostly from the terminal. · Sections: Basics, Cask GUI Apps, Services · e.g. brew install wget, brew uninstall wget, brew update Tue, 21 Jul 2026 00:00:00 GMT homebrew https://laohand.com/pandoc.html https://laohand.com/pandoc.html Copy-pasting a document between formats usually destroys the structure you worked for. Pandoc converts between Markdown, HTML, PDF, DOCX and EPUB by mapping to a document model, so headings, tables and citations survive. This reference covers basic interchange, Chinese-PDF fonts, templates/styles, slides, e-books and citations/math. Use it when your CMS, wiki or client insists on a format you don't author in. After reading you move content across formats with markup intact. · Sections: Basic Conversion, PDF Advanced Options, Templates & Styles · e.g. pandoc input.md -o output.html, pandoc input.md -o output.pdf, pandoc input.md -o output.docx Tue, 21 Jul 2026 00:00:00 GMT pandoc https://laohand.com/chatgpt.html https://laohand.com/chatgpt.html The gap between a vague ask and a usable result is usually a prompt-structure gap. This reference organizes role setting, task scaffolding, output constraints, few-shot examples and chain-of-thought into patterns you can reuse, mapped to office, coding and writing workflows. Unlike a raw idea dump, each pattern tells the model who to be, what format to return, and how far to reason. After reading you steer output by adding structure instead of by trial and error. · Sections: Prompting, Code, Writing · e.g. You are a senior Python engineer..., Act as a product manager with 10 years of experience..., Complete the following task step by step:... Tue, 21 Jul 2026 00:00:00 GMT chatgpt https://laohand.com/emacs.html https://laohand.com/emacs.html Emacs is notorious for its 2000+ default commands, but you only need a small set daily. This reference groups file & buffers, movement/editing, search, windows, macros and Org-mode, and first demystifies the C=Ctrl, M=Alt/Meta prefix notation, then the chording of C-x C-s style sequences. Learning it lowers the intimidation of the editor and moves editing into muscle memory. After reading you can open, edit and save files, wrangle buffers, and record a macro without touching the manual. · Sections: Files & Buffers, Cursor Movement, Editing · e.g. C-x C-f, C-x C-s, C-x C-w Tue, 21 Jul 2026 00:00:00 GMT emacs https://laohand.com/vscode.html https://laohand.com/vscode.html VSCode turns refactoring, symbol navigation and multi-cursor editing into pure keyboard work, keeping your attention on the logic instead of the mouse. Ordered by workflow — General, Editing, Navigation, Refactor/Debug, Git — each shortcut lists both macOS and Win/Linux keybindings and calls out the platform deltas (Cmd→Ctrl, Option→Alt). For rename, jump-to-definition and batch editing without the mouse, start with the Command Palette and Editing groups; in cross-platform teams it also helps you align on keybinding docs. After reading you can drive most of a refactoring session from the keyboard. · Sections: General, Editing, Navigation · e.g. Cmd+Shift+P, Ctrl+Shift+P, Cmd+P Tue, 21 Jul 2026 00:00:00 GMT vscode https://laohand.com/pm2.html https://laohand.com/pm2.html Running node app.js in the foreground means watching a process die or a memory leak build with no safety net. PM2 layers on daemon supervision, self-restart, cluster mode, logging and boot-start as one loop. This table is grouped into start/run, logs, monitoring, cluster, startup and ecosystem.config.js, with deployment-critical flags, and it calls out CLI differences like reload vs restart and the pm2 save + startup pair for crash recovery. After reading you can set up supervision, scaling and self-healing for a Node service on your own. · Sections: Start & Stop, Logs, Monitor & Status · e.g. pm2 start app.js, pm2 start app.js --name "api", pm2 start app.js -i max Tue, 21 Jul 2026 00:00:00 GMT node https://laohand.com/ruby.html https://laohand.com/ruby.html This reference is for developers picking up Ruby (including Rails) or recalling its idioms. It starts with variables, symbols, and common built-in methods, then arrays/hashes, control flow (including postfix if and unless), methods and blocks/Proc/Lambda, classes & modules with attr_accessor, include/extend, and inheritance, and ends with begin-rescue-ensure exception handling. Unlike many languages, almost everything in Ruby is an object and methods return the value of their last expression, and blocks elegantly wrap iteration. After reading you should be able to write idiomatic, concise Ruby: iterate with blocks instead of hand loops, use symbols as hash keys, and organize reusable behavior into modules. · Sections: Basics, Array & Hash, Control Flow · e.g. name = "Ruby", name = "Hello, #{name}", :symbol Tue, 21 Jul 2026 00:00:00 GMT ruby https://laohand.com/moment.html https://laohand.com/moment.html This reference is for JavaScript developers doing everyday date work — formatting a timestamp for display, adding days to an expiry, comparing two dates, or showing "3 days ago". It walks creation from strings, timestamps, and object literals (mind the zero-based month), formatting tokens, add/subtract and startOf/endOf snapping, comparison helpers, relative time, and timezone handling with moment-timezone. Note that moment is in maintenance mode; prefer native Date or Day.js for new code. After reading you should be able to parse, format, shift, and compare dates, and render friendly relative strings. · Sections: Creating Dates, Formatting, Manipulating Dates · e.g. moment(), moment("2024-01-15"), moment("2024-01-15", "YYYY-MM-DD") Tue, 21 Jul 2026 00:00:00 GMT javascript https://laohand.com/sinon.html https://laohand.com/sinon.html This reference is for JavaScript developers writing unit tests who need to isolate the code under test from its surroundings. It covers spies for observing calls, stubs to replace behavior with return/throw/resolve constants, strict mocks with expectations, fake timers to fast-forward setTimeout, and sandboxes that auto-restore everything. Later sections show the sinon.assert helpers and practical patterns like sinon.replace and parameter matchers. After reading you should be able to spy on a dependency, stub an external call, control time in tests, and clean up all doubles in a teardown. · Sections: Spy, Stub, Mock · e.g. sinon.spy(obj, "method"), sinon.spy(fn), spy.calledOnce Tue, 21 Jul 2026 00:00:00 GMT javascript https://laohand.com/chai.html https://laohand.com/chai.html This reference is for JavaScript developers writing tests with Mocha, Jest integrations, or plain Node. Chai gives three interchangeable styles (expect, should, assert); this cheatsheet shows the same check written each way. It covers equality, deep comparison of objects/arrays, type and inclusion checks, thrown-error assertions, numeric bounds, and plugin-backed helpers such as eventually (chai-as-promised) and HTTP status (chai-http). After reading you should be able to write readable assertions for values, collections, thrown errors, and promises, and know when deep.equal beats equal. · Sections: Expect Style (BDD), Should Style (BDD), Assert Style (TDD) · e.g. expect(value).to.equal(expected), expect(value).to.be.a("string"), expect(array).to.include(item) Tue, 21 Jul 2026 00:00:00 GMT javascript https://laohand.com/react-router.html https://laohand.com/react-router.html This reference is for React developers wiring up client-side navigation with React Router v6. It covers the declarative Routes/Route tree, nested layouts with Outlet, Link/NavLink and programmatic useNavigate, reading dynamic params and refreshing the query string, guarding protected pages, and the reactive data APIs (loader/action) added in v6.4. Each entry fills a concrete gap, like rendering a 404, keeping nav active state, or redirecting after login. After reading you should be able to declare a route tree, link between pages, handle :id params and ?query, and protect authenticated screens. · Sections: Router Setup, Navigation, Route Params · e.g. <BrowserRouter><App /></BrowserRouter>, <Routes><Route path="/" element={<Home />} /></Routes>, <Route path="/users/:id" element={<User />} /> Tue, 21 Jul 2026 00:00:00 GMT javascript https://laohand.com/redux.html https://laohand.com/redux.html This reference is for React developers who want predictable, central state with the Redux Toolkit. It covers store configuration, createSlice with its auto-generated actions and Immer-powered immutability, async logic via createAsyncThunk with pending/fulfilled/rejected cases, middleware, and the React bindings useSelector/useDispatch. A closing section shows normalized state with createEntityAdapter and a first look at RTK Query. After reading you should be able to set up a slice, dispatch both sync and async actions, read state reactively, and model collections as normalized entities. · Sections: Store Setup, Slice Creation, Actions & Dispatch · e.g. const store = configureStore({ reducer: rootReducer }), configureStore({ reducer: { users: usersReducer, posts: postsReducer } }), configureStore({ middleware: (gdm) => gdm().concat(logger) }) Tue, 21 Jul 2026 00:00:00 GMT javascript https://laohand.com/promise.html https://laohand.com/promise.html This reference is for JavaScript developers writing async code, whether in the browser with fetch or in Node. It starts from creating and consuming a promise, then static combinators — all vs race vs allSettled vs any, which beginners often mix up — before chaining and the async/await sugar it sits on. Later sections cover real problems: running many requests concurrently without flooding, waiting for the fastest result with a timeout, retrying a flaky request, and aborting an in-flight fetch with AbortController. After reading you should be able to sequence async steps, run parallel tasks with a concurrency cap, and add timeout and retry to brittle calls. · Sections: Basics, Consuming Promises, Static Methods · e.g. new Promise((resolve, reject) => { resolve(value) }), new Promise((resolve, reject) => { reject(new Error("fail")) }), Promise.resolve(value) Tue, 21 Jul 2026 00:00:00 GMT javascript https://laohand.com/react.html https://laohand.com/react.html This reference is for React developers who write function components and Hooks. It moves from the state/effect core to advanced hooks such as useReducer, context, and useId, then component patterns like forwardRef and render props, before controlled forms, state via Context, and performance optimizations like React.memo and lazy. Each entry is a copy-ready snippet with the deps array and edge cases called out. After reading you should be able to drive async data with useEffect, share state across components with Context, and stop wasted re-renders with memo/useCallback. · Sections: Core Hooks, Advanced Hooks, Component Patterns · e.g. const [count, setCount] = useState(0), const [user, setUser] = useState({ name: "", age: 0 }), useEffect(() => { fetchData() }, []) Tue, 21 Jul 2026 00:00:00 GMT node https://laohand.com/vue.html https://laohand.com/vue.html This reference targets Vue 3 developers working with the Composition API and <script setup>. It walks from reactivity basics (ref vs reactive) to computed and watchers, then props/emits/provide-inject for component communication, before covering routing, Pinia, templates, and performance tweaks like shallowRef and defineAsyncComponent. Each entry is a snippet you can drop into an existing SFC and observe the reactive update. After reading you should be able to manage local state with ref/reactive, react to changes with watch, wire up a child parent call, and lazy-load heavy components. · Sections: Reactivity Basics, Lifecycle Hooks, Component Communication · e.g. const count = ref(0), count.value++, const state = reactive({ name: "Vue" }) Tue, 21 Jul 2026 00:00:00 GMT node https://laohand.com/lodash.html https://laohand.com/lodash.html This reference is for JS devs who would rather use a well-tested helper than reimplement the same loop by hand. Entries span arrays, objects, strings, collections, and function utilities, with each command showing the exact call that solves a stubborn problem — like reading a deeply nested value that may not exist, deep-cloning to avoid mutating shared state, or debouncing an input handler. Unlike native methods, Lodash versions handle nullish inputs and edge cases for you. After reading you should be able to pick the right helper for dedupe, grouping, debounce, and safe deep merge. · Sections: Array, Object, String · e.g. _.map(arr, (n) => n * 2), _.filter(arr, (n) => n > 0), _.reduce(arr, (sum, n) => sum + n, 0) Tue, 21 Jul 2026 00:00:00 GMT node https://laohand.com/typescript.html https://laohand.com/typescript.html This reference is for JS and frontend developers who want to write clear types in their day-to-day code. Instead of dumping definitions, entries progress from variables to interfaces, generics, and utility types, with each explaining the scenario it solves — such as when to prefer interface over type, how Partial makes form fields optional, and how Pick/Omit carve a subset out of a larger type. After reading you should be able to annotate functions and objects precisely, constrain values with literal unions, and use utility types to tighten your options. · Sections: Basic Types, Interfaces & Types, Generics · e.g. let name: string = "John", let age: number = 30, let isActive: boolean = true Tue, 21 Jul 2026 00:00:00 GMT node https://laohand.com/matlab.html https://laohand.com/matlab.html This reference is for engineers and scientists who think in matrices rather than element loops. It covers building matrices and vectors, in-place operations like transpose and eigenvalue decomposition, statistical summaries, plotting curves and surfaces, file read/write, and FFT-based signal analysis. Unlike numpy the commands here feel native to the language, so you can type them directly in the Command Window and inspect each result. After reading you should be able to assemble a matrix, transpose/invert/decompose it, turn a vector into a plot, and save the intermediate result with save/load. · Sections: Matrix Creation, Matrix Operations, Data Visualization · e.g. A = [1 2 3; 4 5 6; 7 8 9], B = [1; 2; 3], C = [1, 2, 3] Tue, 21 Jul 2026 00:00:00 GMT language https://laohand.com/ejs.html https://laohand.com/ejs.html This reference is for Node and Express developers who render pages serverside with EJS, the template engine you configure in one line and use everywhere. It covers the tag syntax (<% code %>, <%= escaped output %>, <%- raw HTML %>, <%- include %>, comments), how to branch and loop over the locals you pass in, splitting pages into includes, sharing a layout, and calling res.render from Express. Unlike a generic EJS primer, entries are grouped by what each part of the template does, and note when output is escaped vs raw. After reading you should be able to build an Express view, loop over data with <%- for %>, escape user content with <%=, and reuse header/footer via includes. · Sections: Basic Syntax, Conditionals, Loops · e.g. <% code %>, <%= value %>, <%- value %> Tue, 21 Jul 2026 00:00:00 GMT language https://laohand.com/dart.html https://laohand.com/dart.html This reference is for Dart developers building Flutter apps or backend services, centered on the syntax you write all day: null-safe variables (final/const vs late), functions and closures, classes with mixins, and async flow with Future/async/await. Unlike a flat Dart feature list, entries are grouped by the construct and flag null-safety behavior that trips people new from Java/JS. After reading you should be able to write null-safe chains without non-null assertions everywhere, compose classes with mixins, and handle asynchronous work with Future and async/await without blocking the UI thread. · Sections: Variables & Types, Functions & Closures, Classes & Mixins · e.g. var name = 'Dart';, String name = 'Dart';, final name = 'Dart'; Tue, 21 Jul 2026 00:00:00 GMT dart https://laohand.com/csharp.html https://laohand.com/csharp.html This reference is for .NET developers building web APIs, services, or desktop apps, focusing on the C# syntax you write every day: classes and interfaces with their access modifiers, LINQ for querying collections instead of hand-written loops, async/await for I/O-bound work, generics and delegates, and the property/event model. Unlike a flat C# feature list, entries are grouped by the language construct and note where C# behavior differs from Java or JS. After reading you should be able to replace a nested loop with a composed LINQ query, set up an async method without deadlocking, and design a type with properties, events and a delegate. · Sections: Classes & Interfaces, Properties & Methods, LINQ Queries · e.g. public class MyClass { }, public interface IMyInterface { void Method(); }, public class Derived : Base, IMyInterface { } Tue, 21 Jul 2026 00:00:00 GMT csharp https://laohand.com/cpp.html https://laohand.com/cpp.html This reference is for C++ developers writing applications, games, or libraries, organized around modern C++ — where smart pointers, the STL, and lambdas drastically reduce the manual-lifetime bugs C++ is famous for. It covers classes and objects with their access control, the go-to STL containers and when each fits, smart pointers vs raw new/delete, lambda captures, function and class templates, and exceptions. Unlike a flat C++ feature list, entries are grouped by the construct you are writing and flag RAII-versus-manual-ownership choices. After reading you should be able to reach for std::vector/std::map instead of raw arrays, prefer unique_ptr over naked new, and write a templated function or lambda capture-free of leaks. · Sections: Classes & Objects, STL Containers, Smart Pointers · e.g. class MyClass { public: MyClass(); ~MyClass(); };, struct MyStruct { int x; int y; };, MyClass obj; Tue, 21 Jul 2026 00:00:00 GMT cpp https://laohand.com/c.html https://laohand.com/c.html This reference is for developers writing C for embedded, OS, or performance-critical work, where unlike managed languages you own memory and pointer lifetimes. It covers data types and constants, control flow, pointers and arrays (where the footguns live), functions, manual allocation and freeing, file I/O, and the preprocessor. Entries are grouped by the build block you are working in, with notes flagging where behavior is easy to get wrong. After reading you should be able to decide when to use a pointer vs an array, manage malloc/free without leaks, and encode compile-time logic with #ifdef. · Sections: Data Types & Variables, Control Flow, Pointers & Arrays · e.g. int x = 10;, float pi = 3.14f;, double e = 2.718; Tue, 21 Jul 2026 00:00:00 GMT c https://laohand.com/graphql.html https://laohand.com/graphql.html This reference is for developers designing a GraphQL schema or consuming one from Apollo/URQL/etc. It covers the client-facing vocabulary first — querying exactly the fields you want, mutating data, subscribing to updates, and reusing fragments — then the schema side from the type system and directives to pagination and the introspection __typename. Unlike a generic syntax sheet, items are grouped by the role you are playing in an API conversation. After reading you should be able to shape a precise query with arguments and fragments, declare a type with the right scalar/object fields, and add a connection-style paginated field. · Sections: Query, Mutation, Subscription · e.g. { user { id name } }, { user(id: 1) { name } }, { users { id name posts { title } } } Tue, 21 Jul 2026 00:00:00 GMT graphql https://laohand.com/jquery.html https://laohand.com/jquery.html This reference is for developers who maintain older codebases or browser extensions still built on jQuery, covering the API that lives in every such file: selectors, reading and writing DOM content and attributes, class toggling, event binding and delegation, Ajax shorthand, and simple animations. Unlike a flat jQuery API dump, entries are grouped by the interaction they perform — find elements, manipulate them, respond to events, or fetch data. After reading you should be able to chain a selector into DOM edits, delegate events to stay fast on dynamic lists, and replace a page refresh with an Ajax request. · Sections: Selectors, DOM Manipulation, Event Binding · e.g. $("div"), $(".class"), $("#id") Tue, 21 Jul 2026 00:00:00 GMT jquery https://laohand.com/es6.html https://laohand.com/es6.html This reference is for JavaScript developers who want to write modern code instead of callback-and-var-era patterns, covering the ES2015+ features that reshaped daily use: let/const block scoping, arrow functions, destructuring, template literals, Promise/async flow, import/export modules, classes, Map/Set, and iterators. Unlike a dry spec list, entries are grouped by the situation each feature fixes — scope confusion, unwieldy callbacks, or verbose object access. After reading you should be able to replace var with block-scoped bindings, flatten nested callbacks with async/await, and structure multi-file projects with import/export. · Sections: Variables & Functions, Destructuring, Asynchronous · e.g. let x = 1, const PI = 3.14, const fn = (x) => x * 2 Tue, 21 Jul 2026 00:00:00 GMT es6 https://laohand.com/express.html https://laohand.com/express.html This reference is for Node.js developers building REST APIs and web apps on Express, from a small internal service to a full EJS-rendered site. It covers the app/router setup, defining routes with params/query, reading the request and shaping the response, wiring the middleware ecosystem (express.json, static, cors, helmet, morgan, compression), serving EJS views, adding JWT auth, and the async error-handling pattern. Unlike a generic Express snippet list, entries are grouped by the layer of the request lifecycle you are working on. After reading you should be able to stand up an app, mount routers and middleware in the right order, and centralize async error handling instead of scattering try/catch. · Sections: App Setup, Route Definition, Request Object · e.g. const app = express(), app.use(express.json()), app.listen(3000, () => {}) Tue, 21 Jul 2026 00:00:00 GMT express https://laohand.com/laravel.html https://laohand.com/laravel.html This reference is for developers building Laravel applications and the people deploying them, centering on Artisan, the CLI you run constantly. It covers scaffolding a project, generating models/controllers/migrations, running and rolling back migrations, boosting production with route/config/view caching, and handling background work with the queue. Unlike a generic Artisan command dump, entries are grouped by the workflow you actually repeat: create feature → migrate DB → run locally → cache for prod → queue the heavy work. After reading, you should be able to scaffold a CRUD feature, apply and roll back migrations cleanly, and be confident about what each cache command commits or clears. · Sections: Project & Dev, Database, Routes & Cache · e.g. laravel new project, php artisan serve, php artisan make:model Post -mcr Tue, 21 Jul 2026 00:00:00 GMT laravel https://laohand.com/swift.html https://laohand.com/swift.html This reference is for Swift developers shipping iOS/macOS apps, command-line tools, or server code, spanning the two toolchains you bounce between: the Swift/SwiftPM CLI and xcodebuild/xcrun simctl. It covers compiling and running scripts, initializing and building Swift packages, building/testing/archiving a scheme, driving simulators, and the syntax idioms (let/var, optional binding, map/filter/reduce) plus debug/assert helpers you reach for daily. Unlike a flat Swift command list, entries are grouped by the actual cycle of compile → test → archive → run on simulator. After reading, you should be able to take a package from swift package init to a passing swift test, and drive an Xcode scheme from the terminal. · Sections: Compile & Run, Swift Package Manager, Xcode CLI · e.g. swift main.swift, swiftc main.swift -o main, swift main.swiftc Tue, 21 Jul 2026 00:00:00 GMT swift https://laohand.com/kotlin.html https://laohand.com/kotlin.html This reference is for Kotlin developers — on Android, a JVM backend, or experimenting with scripts — and covers the five things you touch constantly: compiling and running with kotlinc/Gradle, null-safety idioms (safe-call, elvis, the non-null assertion), collection operators like filter/map/groupBy, and coroutines for structured concurrency. Unlike a generic Kotlin grammar dump, entries are grouped by the problem each snippet solves, from "avoid the NPE" to "run I/O off the main thread". After reading, you should be able to write null-safe chains without !! except where intended, transform collections fluently, and launch coroutines scoped so cancellation propagates correctly. · Sections: Compile & Run, Gradle Build, Null Safety · e.g. kotlinc main.kt -include-runtime -d main.jar, java -jar main.jar, kotlinc -script script.kts Tue, 21 Jul 2026 00:00:00 GMT kotlin https://laohand.com/rust.html https://laohand.com/rust.html This reference is for Rust developers — whether you are still wrestling with the borrow checker or shipping a production crate — and centers on Cargo, the toolchain you touch every day. It covers scaffolding projects, building (debug vs release), running binaries, testing, generating docs, running Clippy lints, formatting with rustfmt, and cross-compiling for a target. Unlike a flat list of cargo subcommands, entries follow the workflow you actually repeat: edit → check/build → test → lint → fmt → release. After reading, you should be able to take a fresh crate from cargo new through a clean Clippy + test pass to a release build. · Sections: Project Management, Dependency Management, Testing & Docs · e.g. cargo new project_name, cargo new --lib project_name, cargo init Tue, 21 Jul 2026 00:00:00 GMT rust https://laohand.com/php.html https://laohand.com/php.html This reference is for developers writing PHP apps and the people who deploy and operate them, running everything from single scripts to Laravel projects. It covers executing code on the CLI, the built-in dev server, Composer dependency and autoload management, extension/ini checks, and the php -l lint gate. Unlike a generic PHP command dump, entries are grouped by the workflow you actually repeat when scaffolding, debugging, and shipping a PHP application. After reading, you should be able to boot a Composer-based project locally, keep its autoload in sync, and gate merges on a lint pass. · Sections: CLI Run, Composer Dependency, Extensions & Config · e.g. php script.php, php -a, php -S localhost:8000 Tue, 21 Jul 2026 00:00:00 GMT php https://laohand.com/java.html https://laohand.com/java.html This reference is for developers writing Spring Boot/WAR apps or operating them in production: from compiling and packing with javac/java/jar, one-command builds with Maven/Gradle, heap sizing with -Xms/-Xmx, G1 GC and GC logging, to grabbing threads and heap with jstack/jmap/jstat when the service stalls. Unlike a generic command list, it is organized around building the service, running it stably, tuning it faster, and debugging its failures. After reading you should be able to complete a build → deploy → GC tune → deadlock hunt cycle on your own. · Sections: Compile & Run, Maven Commands, Gradle Commands · e.g. javac Main.java, java -cp .:lib.jar Main, java -cp ".;lib.jar" Main Tue, 21 Jul 2026 00:00:00 GMT java https://laohand.com/numpy.html https://laohand.com/numpy.html This reference is for developers who frequently process arrays in Python, from quick data cleaning to embedding matrix math: creating arrays with np.array/np.zeros, pulling out data by index and slice, reshaping, drawing statistics with sum/mean, and matrix multiplication with a @ b. Unlike a bare API manual, entries follow the practical chain of create → select → reshape → compute → save. After reading you should be able to pick the right function for each stage and dodge the most common broadcast and view-vs-copy pitfalls. · Sections: Array Creation, Indexing & Slicing, Shape Manipulation · e.g. np.array([1, 2, 3]), np.zeros((3, 4)), np.ones((2, 3)) Tue, 21 Jul 2026 00:00:00 GMT numpy https://laohand.com/go.html https://laohand.com/go.html This reference is for developers writing Go API services, concurrent workers, or ops tooling, collecting the most common syntax skeletons: variable declarations, loops and branches, functions and defer, struct methods, interfaces, and the goroutine/channel concurrency that is easiest to get wrong. Unlike bare API docs, entries give copy-ready snippets grouped by the problem each solves. After reading you should be able to write concurrency with goroutines + a WaitGroup, abstract dependencies through interfaces, and check errors Go-style with err != nil. · Sections: Variables & Constants, Control Flow, Functions · e.g. var name string = "value", name := "value", const Pi = 3.14 Tue, 21 Jul 2026 00:00:00 GMT language https://laohand.com/javascript.html https://laohand.com/javascript.html This reference serves developers building React/Vue, Node scripts, or any frontend project, focusing on the ES6+ syntax used daily: variables & functions, destructuring, template strings, higher-order array methods, async, and modules. Unlike docs that list APIs by name, entries here are grouped by the problem each snippet solves, so you can copy as you go. After reading you should be able to write block-scoped variables without var, pull values out with destructuring, replace handwritten for loops with map/filter, and tidy up callbacks with async/await. · Sections: Variables & Functions, Destructuring, String & Template · e.g. const name = "value", let count = 0, const fn = (x) => x * 2 Tue, 21 Jul 2026 00:00:00 GMT language https://laohand.com/python.html https://laohand.com/python.html This reference is for developers who are new to Python or hop between projects, covering the syntax you reach for most when scripting, processing text and data, and automating small tasks. Unlike API listings, entries are grouped by real usage scenarios (environments, containers, file I/O, exceptions) so you can code directly. By the end you should be able to set up a venv, condense loops into comprehensions, read and write files and JSON safely, and contain runtime errors with try/except. · Sections: Virtual Environment & Package Management, Data Types, List Comprehension · e.g. python3 -m venv venv, source venv/bin/activate, venv\Scripts\activate Tue, 21 Jul 2026 00:00:00 GMT language https://laohand.com/sqlite.html https://laohand.com/sqlite.html For developers who need a zero-config, single-file, fast-enough embedded database. SQLite needs no server or credentials; a single .db file moves anywhere. The trade-off is that only one writer is allowed at a time across the whole file, so concurrent writes need WAL mode and a busy timeout. By the end you can create databases and tables, constrain data with indexes and constraints, import and export CSV, and enable WAL to improve concurrent read/write behavior. · Sections: Database Connection & Basics, Table Operations, Data CRUD · e.g. sqlite3 file.db, .open file.db, .databases Tue, 21 Jul 2026 00:00:00 GMT database https://laohand.com/knex.html https://laohand.com/knex.html For Node.js developers who want to write SQL fluently in JavaScript and switch databases without rewriting queries. The value of Knex-transpiled is a chainable API with automatic parameter binding, but you must call .then/await for it to execute and understand when a raw() escape hatch beats the builder. By the end you can build CRUD, joins, and groupBy chains deterministically, wrap multi-statement logic in a transaction with rollback, and confirm the generated SQL with debug/toString. · Sections: Query Data, Insert Data, Update & Delete · e.g. knex("users").select("*"), knex("users").select("name", "email"), knex("users").where("age", ">", 18) Tue, 21 Jul 2026 00:00:00 GMT database https://laohand.com/sql-join.html https://laohand.com/sql-join.html For developers who join tables but still get the row counts wrong. The recurring trap is that a JOIN on a one-to-many parent duplicates parent rows, inflating results unless you dedupe. By the end you can pick INNER vs LEFT by whether un-matched rows should survive, understand the duplication pitfall on one-to-many joins, express candidate-missing conditions with LEFT JOIN ... WHERE ... IS NULL, and choose EXISTS for correlated subqueries. · Sections: INNER JOIN, LEFT / RIGHT JOIN, FULL / CROSS JOIN · e.g. SELECT * FROM users INNER JOIN orders ON users.id = orders.user_id, SELECT u.name, o.total FROM users u JOIN orders o ON u.id = o.user_id, SELECT u.name, o.total FROM users u JOIN orders o ON u.id = o.user_id AND o.status = 'paid' Tue, 21 Jul 2026 00:00:00 GMT database https://laohand.com/neo4j.html https://laohand.com/neo4j.html For developers modeling connected data — friends, dependencies, fraud rings — where a JOIN would be clumsy. Cypher is ASCII-art patterns that read as the shape of the graph you want. By the end you can create nodes and typed relationships, query multi-hop patterns with variable-length paths, enforce uniqueness with constraints and speed lookups with indexes, and aggregate over matched paths. · Sections: Create Nodes & Relationships, Query & Match, WITH & Subqueries · e.g. CREATE (n:Person {name: "Alice"}), CREATE (a:Person)-[:KNOWS]->(b:Person), CREATE (a:Person {name: "Alice"})-[:KNOWS {since: 2020}]->(b:Person {name: "Bob"}) Tue, 21 Jul 2026 00:00:00 GMT neo4j https://laohand.com/mongodb.html https://laohand.com/mongodb.html For backend developers using a document store where reads must stay fast. MongoDB shines at schemaless flexible documents, but that freedom costs you unless you index the fields you filter on. By the end you can design CRUD queries against a collection, read explain("executionStats") to confirm an index is used, build an aggregation pipeline with match/group/sort, and know what a replica set guarantees versus what requires sharding. · Sections: Database, Document CRUD, Query Operators · e.g. show dbs, use dbname, db Tue, 21 Jul 2026 00:00:00 GMT database https://laohand.com/redis.html https://laohand.com/redis.html For developers using Redis as a cache who must care about memory and TTL strategy. The commands are easy, but big keys blowing up memory, hot keys concentrating load on one node, and cache penetration/avalanche are the real business problems. By the end you can pick the right command per data structure, use INFO memory and object encoding to find top memory consumers, understand the RDB/AOF persistence trade-off, and use SCAN/UNLINK to handle big keys without blocking the instance. · Sections: Connection, Data Structure, Key Space · e.g. redis-cli -h 127.0.0.1 -p 6379 -a password, redis-cli --scan --pattern "user:*", redis-cli -r 5 -i 1 INFO memory Tue, 21 Jul 2026 00:00:00 GMT redis https://laohand.com/postgresql.html https://laohand.com/postgresql.html For anyone connecting, analyzing queries, or resolving lock issues on PostgreSQL. Its strength is MVCC and a rich type/index ecosystem, but that also brings lock waits, VACUUM, and table bloat unique to it. By the end you can manage roles and databases with psql, use EXPLAIN ANALYZE to see whether cost comes from a sequential scan or an index, locate lock waits and deadlocks in pg_locks, and migrate or restore across instances with pg_dump/pg_restore. · Sections: Connection & Role, Database & Table, Query Analysis · e.g. psql -U postgres -h 127.0.0.1 -p 5432, psql -U postgres -d db_name -c "\dt", CREATE ROLE app_user WITH LOGIN PASSWORD 'secret'; Tue, 21 Jul 2026 00:00:00 GMT database https://laohand.com/mysql.html https://laohand.com/mysql.html For anyone creating databases, optimizing slow queries, or backing up MySQL. The key is not typing CRUD but understanding whether a WHERE hits an index, what EXPLAIN type means, and that DDL and bulk operations can lock tables and stall production. By the end you can use EXPLAIN to judge whether a query uses an index and spot full table scans (type=ALL), grant least-privilege accounts safely, take restorable backup with mysqldump, and recognize where replication can stall. · Sections: Connection & User, Database & Table, Query & Index · e.g. mysql -u root -p -h 127.0.0.1 -P 3306, mysql -u root -p db_name < dump.sql, mysqldump -u root -p --single-transaction db_name > backup.sql Tue, 21 Jul 2026 00:00:00 GMT database https://laohand.com/elasticsearch-commands.html https://laohand.com/elasticsearch-commands.html For operators and search engineers who must keep a cluster green and answer "why is this index slow or unassigned". The hard part is interpreting health, what drives shard relocation, and ILM policy trade-offs. By the end you can check cluster status, find and diagnose red/unassigned shards, manage index aliases and lifecycle, issue term/range/multi-search queries, and trace slow queries and disk pressure. · Sections: Cluster Status, Shard & Index, Document CRUD · e.g. curl localhost:9200/_cluster/health?pretty, curl localhost:9200/_cat/nodes?v, curl localhost:9200/_cat/health?v Tue, 21 Jul 2026 00:00:00 GMT search https://laohand.com/svelte.html https://laohand.com/svelte.html For frontend developers who want less boilerplate and a minimal runtime. Svelte compiles reactivity directly into native DOM updates at build time, so the runtime is tiny and there is no virtual-DOM mental model; but it lives on assignment-driven updates, $: recomputation, and Store subscriptions that take getting used to. By the end you can declare reactive state with let and $:, communicate between components via events and dispatch, share cross-component state with Store, and hook into lifecycle and transitions. · Sections: Template Syntax, Reactive Declarations, Components & Props · e.g. { expression }, {@html rawHtmlString}, {#if condition}...{:else if}...{:else}...{/if} Tue, 21 Jul 2026 00:00:00 GMT frontend https://laohand.com/nextjs.html https://laohand.com/nextjs.html For React developers building full-stack apps who must decide between SSR and SSG. The core of Next.js is not a list of APIs but clarifying who renders on the server, what interacts on the client, and when data goes stale — server components cannot attach onClick, and ISR serves cached data that can lag behind. By the end you can build a practical App Router page and layout, draw the client/server component boundary, weigh static generation vs ISR, and handle middleware and data fetching. · Sections: App Router Basics, Routing & Navigation, Data Fetching · e.g. app/page.tsx, app/layout.tsx, app/loading.tsx Tue, 21 Jul 2026 00:00:00 GMT frontend https://laohand.com/tailwind-css.html https://laohand.com/tailwind-css.html For developers adopting atomic CSS who prefer not to write large stylesheet files. Tailwind folds styles into composable utility classes and, with JIT, emits only what is used — which means you must grasp breakpoint prefixes, dark-mode variants, and state utilities like group-hover. By the end you can assemble responsive layouts directly, toggle dark mode, control spacing and color, and know why mixed-use with semantic classes needs explicit conventions. · Sections: Layout, Flexbox, Grid · e.g. container, block / inline-block / inline, hidden Tue, 21 Jul 2026 00:00:00 GMT frontend https://laohand.com/html-meta.html https://laohand.com/html-meta.html For developers who want their pages to rank, share cleanly, and be safe. Meta tags are invisible yet decide what search engines index, what a link preview shows on WeChat/Twitter, and how the browser treats the page origin. By the end you can wire up title/description and Open Graph for rich link previews, set viewport for mobile, configure theme-color and a PWA manifest, and add basic Content-Security-Policy guidance. · Sections: Document Metadata, SEO, Social Sharing (Open Graph + Twitter) · e.g. <meta charset="UTF-8">, <meta name="viewport" content="width=device-width, initial-scale=1">, <meta name="description" content="Page description"> Tue, 21 Jul 2026 00:00:00 GMT frontend https://laohand.com/css-grid.html https://laohand.com/css-grid.html For developers building full-page layouts with both rows and columns. Unlike Flexbox, Grid controls both axes at once, so it is the right tool for an app shell or a dashboard with a fixed header and footer. By the end you can define a repeatable template, place items into named areas, size columns with fr units so the layout fills the viewport, and build a responsive grid without hammering media queries. · Sections: Container Definition, Gap & Alignment, Cells & Spans · e.g. display: grid, display: inline-grid, grid-template-columns: 1fr 2fr 1fr Tue, 21 Jul 2026 00:00:00 GMT frontend https://laohand.com/css-flexbox.html https://laohand.com/css-flexbox.html For developers who have fought with floats or inline-block for centering and equal-width rows. Flexbox is the modern way to lay out a single row or column quickly. The recurring confusion is that Flexbox is one-dimensional and that justify-content and align-items act on different axes. By the end you can center anything, build a toolbar and a wrapping card row, and control item sizing with flex-grow/flex-shrink/flex-basis without trial and error. · Sections: Container Properties, Gap & Main-axis Alignment, Cross-axis Alignment · e.g. display: flex, display: inline-flex, flex-direction: row Tue, 21 Jul 2026 00:00:00 GMT frontend https://laohand.com/sass.html https://laohand.com/sass.html For developers whose stylesheets have grown hard to maintain. Sass turns repeated declarations into variables and mixins, so a change in one place propagates everywhere instead of a find-and-replace. By the end you can centralize values and shared snippets in variables and mixins, generate repetitive rules with loops, and reuse layout blocks with @extend without duplicating CSS. · Sections: Variables & Operations, Maps & Color Functions, Nesting · e.g. $primary: #6366f1, color: $primary, $primary: #6366f1 !default Tue, 21 Jul 2026 00:00:00 GMT sass https://laohand.com/emmet.html https://laohand.com/emmet.html For hand-writing HTML in an editor like VSCode. Emmet expands one short abbreviation into a full nested structure, which is a large speed gain if you are not using a GUI page builder. By the end you can type an outline like a nav with nested items and produce complete markup, generate repetitive loops and attributes, and apply CSS shorthands without looking them up. · Sections: HTML Basics, Common HTML Structures, CSS Shorthand · e.g. ! or html:5, div#app, div.container Tue, 21 Jul 2026 00:00:00 GMT emmet https://laohand.com/css3.html https://laohand.com/css3.html For developers who write CSS by hand and want structured, responsive styling. The core skill is not memorizing every property but reasoning about the cascade, the box model, and when Flexbox versus Grid saves you layout pain. By the end you can center and align layouts confidently, build a responsive two-column page, and add purposeful transitions instead of guessing. · Sections: Selectors, Box Model, Layout · e.g. .class, #id, div p Tue, 21 Jul 2026 00:00:00 GMT frontend https://laohand.com/html.html https://laohand.com/html.html For anyone writing web pages by hand without a framework. HTML is the skeleton every page runs on, and choosing semantic tags over plain <div> affects SEO and accessibility. By the end you can lay out a complete page with structure, media, a real <form>, and correct table markup, and know when to prefer a <section>/<article>/<header> instead of <div>. · Sections: Document Structure, Text Formatting, Lists · e.g. <!DOCTYPE html>, <html lang="zh-CN">, <head>...</head> Tue, 21 Jul 2026 00:00:00 GMT frontend https://laohand.com/ssh.html https://laohand.com/ssh.html For developers and ops who want passwordless login, hop through bastion hosts into the internal network, or map a remote port to localhost for debugging. The value of SSH lies in reusing keys and config: pin frequently used Hosts, jump hosts, and port forwards into ~/.ssh/config instead of retyping long argument sets each time. By the end you can generate and correctly permission a key pair for passwordless login, hop through bastions with ProxyJump, and expose a remote service on localhost with -L for debugging. · Sections: Connection & Auth, Key Management, Config File ~/.ssh/config · e.g. ssh user@host, ssh -p 2222 user@host, ssh -i ~/.ssh/id_ed25519 user@host Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/curl.html https://laohand.com/curl.html For developers who need to hit APIs from the shell, reproduce production issues, and see a full HTTP round trip. Browsers cannot express custom headers, POST bodies, or relaxed TLS checks, so curl is the way to take full control of what a request looks like. By the end you can declaratively build requests with bodies/headers/cookies, break down DNS/connect/TTFB timing with -w to find where slowness lives, and use -v to inspect the TLS handshake and redirect chain. · Sections: Basic Requests, Debugging & Details, Proxy & Timeout · e.g. curl https://example.com, curl -X POST https://api.example.com, curl -H "Content-Type: application/json" -H "Authorization: Bearer xxx" https://api.example.com Tue, 21 Jul 2026 00:00:00 GMT curl https://laohand.com/nginx.html https://laohand.com/nginx.html For engineers debugging 502/504s, adjusting location routing, or setting up reverse proxies. The hard part of Nginx is not the sheer number of directives but the details — location matching rules, whether proxy_pass carries a trailing slash, and upstream timeout tuning — which fail silently and only surface as anomalies under traffic. By the end you will validate with nginx -t before reloading, trace upstream errors back to the backend from the error log, and tell apart 502 Bad Gateway from 504 Gateway Timeout. · Sections: Commands & Testing, Location Matching Priority, Reverse Proxy Snippets · e.g. nginx -t, nginx -s reload, nginx -T Tue, 21 Jul 2026 00:00:00 GMT nginx https://laohand.com/powershell.html https://laohand.com/powershell.html For Windows system administration and automation, PowerShell&apos;s object pipeline is the core: cmdlets output objects rather than text, so you filter and act directly on properties. This table covers common cmdlets and their Linux counterparts, file/process/service operations, and Invoke-Command remoting, helping you script daily Windows ops. · Sections: Basic Commands, File & Directory, Content Operations · e.g. Get-Command, Get-Help Get-Process, Get-Member Tue, 21 Jul 2026 00:00:00 GMT sysops https://laohand.com/terraform.html https://laohand.com/terraform.html Terraform's mental model is three storage layers — code in HCL, config through variables and backend, and the live state describing what actually exists. plan versus apply is the rhythm you operate on: plan previews the diff, apply makes it real, and destroy has to be deliberate. This table pairs each command with the state/backend knowledge it depends on so the workflow clicks instead of confusing. · Sections: Core Workflow, State Management, Variables & Outputs · e.g. terraform init, terraform plan, terraform apply Tue, 21 Jul 2026 00:00:00 GMT cicd https://laohand.com/cron.html https://laohand.com/cron.html The five-field syntax is the only hard part: minute hour day-of-month month weekday, with */n stepping and comma lists. After that, most issues are environmental — a missing PATH or env var, or the job running under a different user than you assume. This table ties time syntax to crontab -l/-e/-r, env setup, and log/file checks so a job that "does nothing" becomes diagnosable. · Sections: Schedule Format, Special Strings, System Cron · e.g. * * * * * command, */15 * * * *, 0 */2 * * * Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/rclone.html https://laohand.com/rclone.html Syncing or backing up between S3, OSS, Google Drive, and local directories, rclone unifies 70+ backends; the key thing to watch is the copy-versus-sync difference, since sync deletes extraneous files on the destination. This table covers configuration, copy/sync, checks, and filters — run a --dry-run preview before a real sync. · Sections: Config & Connect, Browse & List, Sync & Copy · e.g. rclone config, rclone config show, rclone listremotes Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/fish-shell.html https://laohand.com/fish-shell.html Fish ships with syntax highlighting, autocompletion, and magic Tab out of the box, making it great for users who do not want to rig their shell. The main switching cost is the syntax differing from Bash — set replaces export, the for loop differs, and so on — so this table lists those differences for an easy migration of habits. · Sections: Variables & Scope, Control Flow, Functions & Aliases · e.g. set name "John", echo $name, set -x PATH /usr/local/bin $PATH Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/vagrant.html https://laohand.com/vagrant.html Vagrant's payoff is reproducibility: commit the Vagrantfile, and `vagrant up` rebuilds the same VM on anyone's laptop. The commands are short — up/ssh/halt/destroy — but the config points that bite are the box version, synced folders, and provisioner ordering. This table pairs the lifecycle commands with those Vagrantfile settings so a fresh clone goes from checkout to running VM in one command. · Sections: VM Lifecycle, Box Management, Vagrantfile · e.g. vagrant init ubuntu/jammy64, vagrant up, vagrant ssh Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/ansible.html https://laohand.com/ansible.html To change configs, install dependencies, or maintain services across dozens of machines, Ansible runs over SSH with no agent and uses declarative idempotent modules — an efficient entry into ops automation. This table goes from one-off ad-hoc commands to Playbook structure and common modules; run ansible --syntax-check and --check as a dry run before actually executing. · Sections: Core Commands, Ad-hoc Commands, Common Modules · e.g. ansible all -m ping, ansible-playbook site.yml, ansible-galaxy init myrole Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/gnupg.html https://laohand.com/gnupg.html The workflow most people actually repeat is: create a keypair once, export your public key to a paste or keyserver, then encrypt to others or sign your own archives. The two details that trip people up are keeping the private key safe and revocable, and knowing who you are encrypting to (their public key, not yours). This table links key lifecycle, encrypt/sign, and verify so PGP work flows end-to-end. · Sections: Key Generation, Import & Export, Encrypt & Decrypt · e.g. gpg --full-generate-key, gpg --quick-generate-key "Name <email>", gpg --list-keys Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/zsh.html https://laohand.com/zsh.html After switching to Zsh, what actually speeds you up day to day is completion, history search aliases, and a custom prompt. This table covers the high-frequency .zshrc settings and common oh-my-zsh plugins and themes; back up .zshrc before editing so you always have a way back. · Sections: Basic Setup, Variables & Arrays, Globbing & Expansion · e.g. chsh -s $(which zsh), source ~/.zshrc, echo $SHELL Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/ffmpeg.html https://laohand.com/ffmpeg.html The move from "I have a video" to "I have the right video" is mostly choosing the right flags: libx264/libx265 for re-encoding, `-c:v copy -c:a copy` to remux instantly without quality loss, and `-ss`/`-to` for cuts. This table sorts those into convert / cut / extract / compress / filter groups, so media commands stay familiar instead of looked up every time. · Sections: Format Conversion, Trim & Crop, Extract & Separate · e.g. ffmpeg -i input.mp4 output.avi, ffmpeg -i input.mp4 -c:v libx264 output.mp4, ffmpeg -i input.mp4 -c:v libx265 output.mp4 Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/taskset.html https://laohand.com/taskset.html When a process shows latency jitter from frequent cross-NUMA memory access on a many-core machine, or you want reduced variance in CPU-bound benchmarks, taskset pins the process to fixed cores. This table explains the -c usage, how to read the current mask, and the caveat that pinning does not always speed things up. · Sections: Basic Usage, CPU Mask & List Format, Pin Running Processes · e.g. taskset -p <pid>, taskset -c -p <pid>, taskset -c 0,1 <command> Tue, 21 Jul 2026 00:00:00 GMT taskset https://laohand.com/netcat.html https://laohand.com/netcat.html The most common netcat workflow is confirming reachability without any listening service — `nc -zv host port` returns cleanly per port and `-w` stops it hanging on a black-hole drop. Pair that with `-l` to build a one-shot listener and the -z/-v/-w flags to bound each probe, and most "is it open / does it respond" questions settle in one line. · Sections: Connectivity Test & Port Scan, File & Data Transfer, Port Listening · e.g. nc -zv host 80, nc -zv host 80 443 8080, nc -zv host 1-1000 Tue, 21 Jul 2026 00:00:00 GMT netcat https://laohand.com/scp-rsync.html https://laohand.com/scp-rsync.html Moving files between servers, scp is simple but always copies everything and restarts on interruption; rsync does incremental transfer and can resume, saving bandwidth and suiting ongoing sync. This table pairs their common flags so you pick the right tool for one-off copies versus recurring sync. · Sections: scp Basics, rsync Basics, rsync Incremental · e.g. scp file user@host:/path, scp user@host:/path/file ., scp -r dir user@host:/path Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/wget.html https://laohand.com/wget.html wget is the most reliable command-line downloader, especially for scripts and unattended runs: -c resumes after interruption, --retry retries automatically, -b runs in the background, and -r mirrors a site recursively. This table covers these high-frequency combos so interrupted downloads restart from where they broke. · Sections: Basic Download, Resume, Recursive · e.g. wget URL, wget -O filename URL, wget -P /path/to/dir URL Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/top.html https://laohand.com/top.html The load-average headline can mislead — a 4-core host can sit at 8.0 without saturating. Real signal comes from the per-process columns and the memory bar: sort by %CPU, watch for D-state (uninterruptible) processes, and check swap pressure. This table covers interactive keys and batch logs so you can watch top and also export and compare evidence. · Sections: top Basics, top Interactive, top Sort & Display · e.g. top, top -d 5, top -p 1234 Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/ps.html https://laohand.com/ps.html Can't see a process, wondering who ate the memory, need a PID — ps is the first step for all of these. Knowing the difference between BSD-style aux and System-V-style -ef, then pairing grep, --sort, and -o custom columns, lets you filter precisely from the noise. · Sections: Basic View, Filter, Custom Format · e.g. ps, ps aux, ps -ef Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/grep.html https://laohand.com/grep.html For pulling errors out of logs or finding every reference to an identifier in a repo, grep is the fastest entry point. Remember -r for recursive, -i for ignore case, -C for context, and -E for extended regex and you cover most searches — and avoid finding a match without any context. · Sections: Basic Search, Recursive, Regular Expression · e.g. grep "pattern" file, grep -i "pattern" file, grep -v "pattern" file Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/sed.html https://laohand.com/sed.html Most sed use collapses to a handful of forms: s/old/new/g for replace, 1,5d and /pattern/d for delete, and -i for in-place edits. The accidental-destruction risk is real, which is why a -i.bak backup and a dry-run habit matter more than the syntax; this table pairs each rewrite with the guard that keeps it safe. · Sections: Substitute, Delete, Insert & Append · e.g. sed 's/old/new/' file, sed 's/old/new/g' file, sed 's/old/new/2' file Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/awk.html https://laohand.com/awk.html awk's killer use case is column-based aggregation: computing response-code proportions from an nginx log or summing and grouping a report is much faster than writing a script. Understanding RS/FS, NR/NF, and how variables print covers about eighty percent of awk. · Sections: Basic Syntax, Built-in Variables, Conditionals · e.g. awk '{print $1}' file, awk -F: '{print $1, $3}' /etc/passwd, awk '{print $1, $NF}' file Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/screen.html https://laohand.com/screen.html The one command you must internalize is the detach/reattach pair — start with `screen -S name`, quit worry-free with Ctrl-a d, and come back later with `screen -r name`. Everything else (windows, splits, -x sharing) builds on that base; this table lays it out so your long jobs keep running after the network drops. · Sections: Session Management, Windows, Split Screen · e.g. screen -S name, screen -ls, screen -r name Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/netstat.html https://laohand.com/netstat.html Two things dominate day-to-day netstat: is anything listening on my port, and how many ESTABLISHED versus TIME_WAIT connections do I have. Combine -a with -p and you get both the listener and the process holding the port; this table covers those checks plus routing and interface stats, so a quick "is it open / is it healthy" triage needs no extra tooling. · Sections: View Connections, Listening Ports, Routing Table & Interface Stats · e.g. netstat, netstat -a, netstat -at Tue, 21 Jul 2026 00:00:00 GMT network https://laohand.com/lsof.html https://laohand.com/lsof.html Lsof's core strength is reversing the questions — give it a port and it names the process, give it a user and it lists every open file. Port-already-in-use, file-held-by-an-old-process, and disk-space-not-released are all the same root cause, a lingering open handle; this table groups lookups by axis and adds +L1 for the deleted-file case so the usual suspects surface quickly. · Sections: By Process, By Port, By File · e.g. lsof -p 1234, lsof -c nginx, lsof -c /^nginx/ Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/find.html https://laohand.com/find.html find is the go-to for locating files, but it recurses everywhere and follows symlinks, which has traps. This table covers filtering by name, type, size, time, and permission, plus using -exec to act on matches — so you use find fast and safely. · Sections: By Name, By Type, By Size · e.g. find . -name "file.txt", find . -iname "file.txt", find . -name "*.log" Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/chmod.html https://laohand.com/chmod.html Scripts always ask for chmod +x, and wrong log-directory permissions break everything — understanding the permission quartet of owner/group/others plus the special bits makes most permission problems obvious at a glance. This table pairs numeric and symbolic forms, covering common combinations and when to use (and the risks of) SUID, SGID, and the sticky bit. · Sections: Permission Bits, Numeric Mode, Symbolic Mode · e.g. r (read), w (write), x (execute) Tue, 21 Jul 2026 00:00:00 GMT sysops https://laohand.com/bash.html https://laohand.com/bash.html Most Bash scripts only need a few patterns done right: quoting and ${VAR:-default} guards, $? and test conditions, for/while loops, and functions instead of copy-paste. This table is the subset you actually reach for while writing or fixing scripts — pair it with `set -euo pipefail` and the script stops being fragile. · Sections: Variables, Conditionals, Loops · e.g. NAME="value", echo $NAME, echo ${NAME} Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/openssl.html https://laohand.com/openssl.html Reinforcing a cert or debugging "handshake failure" means switching between inspection, generation, and TLS tests — OpenSSL covers all three. The recurring pattern is reading back what you just generated to confirm names, validity, and chains; this table keeps those verify loops and the cursor-pointing handshake test together, so cert work becomes a checklist rather than man-page archaeology. · Sections: Inspect Certificate, Remote Check, Generate Certificate · e.g. openssl x509 -in cert.pem -text -noout, openssl x509 -in cert.pem -dates -noout, openssl x509 -in cert.pem -issuer -noout Tue, 21 Jul 2026 00:00:00 GMT security https://laohand.com/tar-compress.html https://laohand.com/tar-compress.html Before backing up a directory, shipping code, or migrating a server, you will pack it with tar. This table makes the create-versus-extract commands for each compression format (-z/-j/-J) unmistakable and covers advanced but frequently-asked cases like excluding files, guarding against accidental directory deletes, and incremental backups. · Sections: Pack & Compress, Extract, List & Test · e.g. tar -cvf archive.tar dir/, tar -czvf archive.tar.gz dir/, tar -cjvf archive.tar.bz2 dir/ Tue, 21 Jul 2026 00:00:00 GMT archive https://laohand.com/text-processing.html https://laohand.com/text-processing.html Rather than memorizing three manuals, remember one division of labor: grep narrows the lines, sed rewrites the values, awk sums or groups the fields. This table gives you the daily-reachable subset of each, plus combined pipelines, so log triage and report building stay a few keystrokes instead of a script. · Sections: grep Match & Search, sed Replace & Edit, awk Extract & Summarize · e.g. grep "error" app.log, grep -i "error" app.log, grep -rn "TODO" src/ Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/tmux.html https://laohand.com/tmux.html Essential tmux commands for remote development. Organized by session, window, pane, copy mode, and configuration — keep sessions alive when connections drop. · Sections: Session, Window, Pane · e.g. tmux new -s mywork, tmux ls, tmux attach -t mywork Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/mq-commands.html https://laohand.com/mq-commands.html Backlog alerts, consumers that stop consuming, connections climbing abnormally — most message-queue incidents can be traced with these commands. Rather than listing random commands, this table is organized around four scenarios: backlog, connections, cluster, and load testing, so you can judge whether you have too few consumers or slow consumers, a leaking connection pool, or an unhealthy broker. · Sections: Kafka, RabbitMQ, RocketMQ · e.g. kafka-consumer-groups.sh --bootstrap-server :9092 --list, kafka-consumer-groups.sh --describe --group <group>, kafka-topics.sh --describe --topic <topic> Tue, 21 Jul 2026 00:00:00 GMT mq https://laohand.com/cicd-commands.html https://laohand.com/cicd-commands.html When CI hangs in pending or a job fails inexplicably, stop editing the YAML over and over — most clues live in runner status, the failed step&apos;s logs, and whether you can reproduce it locally. This table lays out each platform&apos;s debugging entry point: rerun failed jobs, capture build logs, check runners and caches. Working through them beats blind config edits. · Sections: GitHub Actions, GitLab CI, Jenkins · e.g. gh run list --limit 10, gh run view <run-id> --log-failed, gh run rerun <run-id> --failed Tue, 21 Jul 2026 00:00:00 GMT cicd https://laohand.com/crontab.html https://laohand.com/crontab.html The real pain with Cron is not the retry count but an expression that looks right yet never runs — usually the minimal default PATH, unredirected output, or the combined day-of-month and day-of-week rule. This table walks from expression syntax to troubleshooting, with ready-to-adapt examples that get your schedule right the first time. · Sections: Expression Format, Special Characters, Special Time Macros · e.g. * * * * * command, Minute (0-59), Hour (0-23) Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/systemd.html https://laohand.com/systemd.html Even if all you know is systemctl start or stop, it is worth walking through this set — it is the standard way to manage services on systemd distributions. Beyond start/stop and boot-enabling, it covers targeted journal log queries, timer scheduling, resource caps, and the control-group unit tree, answering three common questions: why a service fails to start, where to find its logs, and how to cap CPU or memory. · Sections: Service Management, Status, journalctl · e.g. systemctl start nginx, systemctl stop nginx, systemctl restart nginx Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/vim.html https://laohand.com/vim.html On a headless server, Vim is the tool you cannot avoid for editing config files. These operations cover precise cursor motion, batch replace, block visual editing, and saving with sudo when you forgot to elevate. Spend ten minutes making motion and search/replace muscle memory, then editing nginx or sshd configs gets naturally faster. · Sections: Motion, Edit, Search · e.g. gg / G, 0 / $, w / b Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/linux-troubleshoot.html https://laohand.com/linux-troubleshoot.html When load spikes, a port stops responding, or disk space alarms, drill down layer by layer with this list — processes, network, disk, memory, then logs — each immediately usable. It deliberately flags common misdiagnoses, from deleted files still held open to telling OOM kills from ordinary crashes, so you hit the root cause instead of chasing the wrong lead. · Sections: Process & Load, Port & Network, Disk & Memory · e.g. top -c, ps aux --sort=-%cpu | head, ps aux --sort=-%mem | head Tue, 21 Jul 2026 00:00:00 GMT linux https://laohand.com/git.html https://laohand.com/git.html Git essentials organized into Commit, Branch, Revert, Remote, and History groups: fix a bad commit with amend/restore/reset, untangle branches with reflog/switch/rebase, inspect changes with git log. Each command notes when to use it and when to be careful. · Sections: Commit & Stash, Branch & Merge, Revert & Undo · e.g. git status -s, git add -p, git commit -m "msg" Tue, 21 Jul 2026 00:00:00 GMT git https://laohand.com/dockerfile.html https://laohand.com/dockerfile.html A Dockerfile authority for developers who want their images small, fast to finalize, and without leaked secrets. Beyond listing instructions, it explains why layer ordering and build cache matter, how multi-stage builds keep runtime images lean, and how ADD vs COPY, ENV vs ARG, USER and HEALTHCHECK change security and behavior. By the end you can write a Dockerfile that builds quickly and produces a minimal, production-safe image. · Sections: Base Instructions, Env & Args, File Operations · e.g. FROM node:18-alpine, FROM scratch, WORKDIR /app Tue, 21 Jul 2026 00:00:00 GMT docker https://laohand.com/docker-compose.html https://laohand.com/docker-compose.html For developers who need to bring up, stop, and upgrade a whole stack at once — database, cache, backend, frontend — as a single unit. Compose value is not in the commands themselves but in a single docker-compose.yml that pins down the network, dependencies, and config between services so the whole environment can be started and stopped repeatedly. By the end you can bring the stack up with up, find the failing service with logs, clean up fully (and safely) with down -v, and scale out with --scale. · Sections: Start & Stop, Logs & Status, Config & Build · e.g. docker compose up -d, docker compose up -d --build, docker compose stop Tue, 21 Jul 2026 00:00:00 GMT docker https://laohand.com/kubectl.html https://laohand.com/kubectl.html A kubectl command reference for app developers and cluster operators, covering resource queries, Pod diagnosis, replica scaling, and cluster context management. Unlike reading YAML directly, kubectl is the consistent window into cluster state and change control, letting you quickly localize frequent incidents such as CrashLoopBackOff, Pods stuck in Pending, and failed rollouts. By the end you can run the whole loop yourself: inspect status → check events → read logs → recover or roll back. · Sections: Get Resources, Describe & Diagnose, Scale & Rollout · e.g. kubectl get pods -n prod, kubectl get pods -o wide, kubectl get pods -A Tue, 21 Jul 2026 00:00:00 GMT kubernetes https://laohand.com/docker-cli.html https://laohand.com/docker-cli.html A Docker command reference for app developers and SREs, covering image build, container lifecycle, networks & volumes, Compose orchestration, and resource cleanup. Unlike OS-level container tools, Docker layered images and isolation are what matter when you must debug startup failures, mapping mistakes, or image bloat. By the end you can bring a service up from an image and troubleshoot the three most frequent problems: startup, networking, and disk usage. · Sections: Image, Container, Network & Volume · e.g. docker images, docker pull nginx:alpine, docker build -t app:1.0 . Tue, 21 Jul 2026 00:00:00 GMT docker https://laohand.com/rsync.html https://laohand.com/rsync.html rsync&apos;s strength is transferring only the changed parts; with --delete it mirrors the destination to match the source, making it standard for log backups and site deploys. This table breaks down common flags and especially stresses running --dry-run (and --checksum to see differences) before the real sync to avoid accidental deletions. · Sections: Basic Sync, Transfer Options, Display Options · e.g. rsync -avz ./src /dest, rsync -avz ./src/ /dest, rsync -avz user@host:/remote /local Sun, 19 Jul 2026 00:00:00 GMT linux https://laohand.com/awscli.html https://laohand.com/awscli.html Having clicked the console a few times, you want to codify it — AWS CLI reproduces most console operations as commands you can script. This table covers configure details, EC2 start/stop and query, S3 upload/download/sync, and IAM least-privilege checks, and reminds you to verify which credential source the environment variables point to before batch operations. · Sections: Configure & Auth, EC2 Instances, S3 Storage · e.g. aws configure, aws configure --profile production, aws configure list Sun, 19 Jul 2026 00:00:00 GMT linux https://laohand.com/httpie.html https://laohand.com/httpie.html While debugging REST APIs, HTTPie auto-highlights and formats the request and response, and lets you write query strings with == and headers with :, which reads far better than curl. This table covers GET/POST, JSON sending, form uploads, Basic/Bearer auth, and cross-request session persistence for most integration work. · Sections: Basic Requests, Headers & Params, Auth & Session · e.g. http GET https://api.example.com/users, http https://api.example.com/users, http POST https://api.example.com/users name=John age:=30 Sun, 19 Jul 2026 00:00:00 GMT linux https://laohand.com/makefile.html https://laohand.com/makefile.html Make shaves rebuilds to a minimum because of one idea: a target only reruns when its prerequisites changed. That means rules, not commands, are the thing to learn — pattern rules like %.o: %.c, automatic variables $@ and $^, and declaring .PHONY for the non-file targets. This table keeps those essentials plus the := versus = assignment gotcha in one place. · Sections: Variables & Assignment, Automatic Variables, Rules & Targets · e.g. CC = gcc, CC := gcc, CC ?= gcc Sun, 19 Jul 2026 00:00:00 GMT linux