google-zx-scripting

name: google-zx-scripting description: "Writes and executes JavaScript-based shell scripts using Google's zx library. Use when writing shell scripts, automation, build tools, file processing, CLI tools, deployment scripts, data pipelines, or batch operations. Also covers piping, streams, parallel execution, retries, cross-platform scripting, built-in fs utilities, and minimist argument parsing."

Google ZX Scripting

Use this skill when writing scripts with Google's zx library — the tool that makes shell scripting with JavaScript/TypeScript productive and safe. Read only the reference file(s) needed for the task.

Quick Start

All zx scripts use the lite entry point for portability. Scripts are standalone .mjs files — no project setup required.

#!/usr/bin/env npx zx

import { $, fs, path, glob, chalk } from 'zx/core';

const files = await glob('src/**/*.ts');
await $`eslint ${files}`;

Run directly:

chmod +x script.mjs && ./script.mjs
# or
npx zx script.mjs

Critical Rules

1. Always use zx/core — never bare zx. Avoids the heavy CLI wrapper.
2. Template literals auto-escape — $`echo ${userInput}` is safe. Never manually quote interpolated variables.
3. Arrays expand correctly — $`cmd ${arrayOfArgs}` expands each element as a separate quoted argument.
4. Non-zero exits throw — use .nothrow() to suppress when you expect failures (e.g., grep with no matches).
5. within() for isolation — creates an async scope with its own $.cwd and $.env. Essential for parallel tasks.
6. Pipe with .pipe() — use $`cmd1`.pipe($`cmd2`) instead of shell |.
7. Prefer zx builtins — glob() over find, fs over cat/cp/mv, fetch() over curl.
8. cd() is global — use within() or $({cwd: '/path'}) for scoped directory changes.
9. Scripts must be .mjs — for top-level await support without bundler config.

Reference Map

Task Routing

• Writing a quick one-off command or shell automation -> references/scripting-patterns.md
• Building a build/deploy/CI script -> references/scripting-patterns.md
• Processing files, data, logs, or batch operations -> references/processing-recipes.md
• Need API details for $, pipes, streams, config -> references/core-api.md
• Combining multiple patterns (e.g., build + process) -> read both relevant files

Import Cheatsheet

// Core — always start here
import { $, fs, path, glob, chalk } from 'zx/core';

// Additional utilities (import individually as needed)
import { spinner, retry, question, echo, sleep, within,
         stdin, tmpdir, tmpfile, which, ps, kill,
         quote, YAML, argv, fetch } from 'zx/core';

Validation Checkpoints

Before executing destructive or bulk operations, always verify scope:

// Verify glob matches before bulk processing
const files = await glob('src/**/*.ts');
console.log(`Found ${files.length} files`);
if (files.length === 0) throw new Error('No files matched — check glob pattern');
if (files.length > 500) throw new Error(`Too many files (${files.length}) — narrow the glob`);

// Dry-run flag for destructive operations
const dryRun = argv['dry-run'] ?? false;
for (const file of files) {
    if (dryRun) { console.log(`[dry-run] would delete ${file}`); continue; }
    await fs.rm(file);
}

For parallel operations, use Promise.allSettled() to handle partial failures:

const results = await Promise.allSettled(
    files.map(f => within(async () => $`process ${f}`))
);
const failed = results.filter(r => r.status === 'rejected');
if (failed.length > 0) {
    console.error(chalk.red(`${failed.length}/${results.length} tasks failed`));
    failed.forEach(r => console.error(r.reason));
    process.exitCode = 1;
}

Conventions for Generated Scripts

1. Shebang line: Always include #!/usr/bin/env npx zx as the first line
2. Verbose off: Set $.verbose = false before main logic to suppress command echoing
3. Error handling: Use the main().catch() pattern — wrap logic in async function main(), then call main().catch(err => { console.error(chalk.red(err.message)); process.exit(1); })
4. Output colors: Use chalk.green() for success, chalk.red() for errors, chalk.yellow() for warnings, chalk.dim() for secondary info
5. Progress: Use spinner() for long-running operations in interactive contexts
6. Arguments: Use argv (pre-parsed minimist) for CLI argument handling
7. Temp files: Use tmpdir() and tmpfile() — they auto-clean on exit
8. Parallelism: Use Promise.all() with within() for parallel operations that need isolation