grep

name	grep
description	Finding text on disk — use ack, not grep (grep is only for filtering the piped output of other commands). Conventions for fast, correct file-content search across a codebase.

Grep

Convention

Use ack for file searching. Use grep only for pipes.

When to Use ack

Use ack whenever searching for patterns in files on disk:

# Search for pattern in current directory and subdirectories
ack "pattern"

# Search with case-insensitivity
ack -i "pattern"

# Search only specific file types
ack --python "pattern"
ack --js "pattern"

# Search with context lines
ack -C 3 "pattern"

# List files that would be searched
ack -f

Why ack:

• Automatically respects .gitignore and .ackrc
• Defaults to recursive search
• Smart file type detection
• Better default output formatting
• Excludes binary files and common build artifacts by default
• Long lines (e.g. jsonl) are automatically truncated and centred on the match. Use jq for structured JSON searching.

When to Use grep

Use grep ONLY for filtering output from other commands:

# Filter command output
ps aux | grep nginx
docker ps | grep -v CONTAINER
journalctl -f | grep error

# Filter file content passed via stdin
cat file.txt | grep pattern

Never use grep for file searching:

# WRONG - searching files with grep
grep -r "pattern" .

# RIGHT - use ack instead
ack "pattern"

ripgrep (rg) — fast, but different defaults and a flag trap

rg is much faster than ack and fine to reach for — but don't assume its flags or filtering match ack's:

• -r means --replace, not "recursive". rg is recursive by default. rg -rn X parses as -r n → "replace every match with the string n", so matches print mangled: VoiceOverlay → nOverlay, seekTo → n. It looks like a display/pipe bug; it is self-inflicted. For line numbers use -n (or --line-number); recursion needs no flag. (Bit me 2026-07-07 — I misfiled it as a foci output bug.)
• Filtering isn't ack's. rg honours .gitignore/.ignore and skips hidden files + binaries by default; ack skips build artifacts via its own built-in list but shows hidden dotfiles. So outside a git repo rg won't auto-skip build dirs, and inside one it hides dotfiles ack would surface — pick per what you're hunting (rg -uu disables the ignore/hidden filtering; ack -f lists what ack would search).
• File-type filters differ: ack --python/--js vs rg -t py/-t js.

Configuration

Local .ackrc files affect searches run from that directory (based on pwd), not searches looking into that directory from elsewhere.