Search & Regex

Q: rg or git grep?

rg for speed and ignore rules; git grep when searching only committed snapshots at specific revision.

Q: Multiline regex?

rg -U multiline mode for cross-line patterns - use sparingly.

Q: find mtime vs atime?

mtime file content change; atime access (often disabled on servers for performance).

Q: sed GNU vs BSD on Mac?

macOS sed requires backup extension sed -i '' - test on target OS.

Q: Exclude venv from grep?

rg auto-ignores; for grep use --exclude-dir=.venv.

Q: Count matches?

rg -c pattern per file or rg pattern | wc -l.

Q: Search compressed logs?

zgrep / zcat file.gz | rg pattern.

Q: Parallel find delete?

Avoid find -delete at scale without -print dry run first.

Q: Regex in Python vs shell?

Prefer Python re in application code; shell regex for operator one-offs only.

grep, ripgrep (rg), find, sed, and awk - the Linux text search toolkit Python developers use to grep logs, locate files, and one-shot transform configs on servers.

Recipe

rg "TaxCalculator" src/
rg -n "raise_for_status" --type py
find /var/log/myapp -name "*.log" -mtime +7
grep -E "ERROR|CRITICAL" /var/log/myapp/app.log | tail -50

When to reach for this:

Find symbol definition across Python monorepo
Search production logs for trace id
Locate large or old files before cleanup
Quick field extraction from CSV/log lines

Working Example

# Find all TODO(FIXME) in Python sources
rg -n "TODO|FIXME" -g "*.py" src/ tests/
 
# Find config referencing old Redis host
rg -l "redis://legacy" --glob "!uv.lock"
 
# Logs: errors in last hour with request id
journalctl -u billing-api --since "1 hour ago" | rg "request_id=550e8400"
 
# Delete stale rotated logs older than 14 days (dry run first)
find /var/log/billing-api -name "*.log.*" -mtime +14 -print

What this demonstrates:

rg type and glob filters reduce noise
-l lists files only for bulk replace planning
journalctl piped to rg for structured grep
find -print before -delete safety

Deep Dive

How It Works

grep - Line-oriented regex match; -r recursive (slow on big trees).
ripgrep - Parallel, gitignore-aware, default for code search.
find - Directory traversal by name, time, size, type.
sed - Stream editor for substitute/delete lines.
awk - Column-oriented processing.

Tool Picker

Task	Tool
Code symbol search	`rg pattern src/`
JSON logs	`jq` (preferred) or `rg` on key
File by name	`find . -name '*.py'`
In-place replace	`sed -i.bak` with backup
CSV 3rd column	`awk -F, '{print $3}'`

Python Notes

# Equivalent to rg for one file with line numbers
grep -n "def main" src/app/cli.py
 
# Find empty __init__.py markers
find src -name "__init__.py" -empty

Gotchas

grep -r from / - IO storm and permission errors. Fix: always start from project or /var/log/app.
sed -i without backup on prod - Broken config unrecoverable. Fix: -i.bak or edit locally + deploy.
Regex greediness - Wrong sed matches multiline config. Fix: test on copy; prefer rg locate + manual edit for critical files.
Ignoring binary matches - grep prints "Binary file matches". Fix: rg or grep -I.
Locale breaks character classes - Unexpected sort/match. Fix: LC_ALL=C for ASCII logs.
Awk on JSON - Fragile vs nested objects. Fix: jq for JSON logs.

Alternatives

Alternative	Use When	Don't Use When
IDE search	Local refactor	SSH-only prod logs
`git grep`	Tracked files only	Generated or log files
`ag` / `ack`	Legacy environments	`rg` available
Python script	Complex parsing	One-liner faster in shell

FAQs

rg or git grep?

rg for speed and ignore rules; git grep when searching only committed snapshots at specific revision.

Case insensitive search?

rg -i pattern or grep -i.

Multiline regex?

rg -U multiline mode for cross-line patterns - use sparingly.

find mtime vs atime?

mtime file content change; atime access (often disabled on servers for performance).

sed GNU vs BSD on Mac?

macOS sed requires backup extension sed -i '' - test on target OS.

Exclude venv from grep?

rg auto-ignores; for grep use --exclude-dir=.venv.

Count matches?

rg -c pattern per file or rg pattern | wc -l.

Search compressed logs?

zgrep / zcat file.gz | rg pattern.

Parallel find delete?

Avoid find -delete at scale without -print dry run first.

Regex in Python vs shell?

Prefer Python re in application code; shell regex for operator one-offs only.

re - Regular Expressions - Python regex
Pipes & Text Processing - composing tools
Parsing Logs and Text - log pipelines
Shell Productivity - aliases for search

Stack versions: This page was written for Python 3.14.0 (stable 3.14, maintenance 3.13), FastAPI 0.115+, Django 5.2, Flask 3.1, Pydantic 2, PyTorch 2.6+, pandas 2.2+, Polars 1.x, ruff 0.9+, and uv 0.6+.

Recipe

rg "TaxCalculator" src/
rg -n "raise_for_status" --type py
find /var/log/myapp -name "*.log" -mtime +7
grep -E "ERROR|CRITICAL" /var/log/myapp/app.log | tail -50

When to reach for this:

Find symbol definition across Python monorepo
Search production logs for trace id
Locate large or old files before cleanup
Quick field extraction from CSV/log lines

Working Example

# Find all TODO(FIXME) in Python sources
rg -n "TODO|FIXME" -g "*.py" src/ tests/
 
# Find config referencing old Redis host
rg -l "redis://legacy" --glob "!uv.lock"
 
# Logs: errors in last hour with request id
journalctl -u billing-api --since "1 hour ago" | rg "request_id=550e8400"
 
# Delete stale rotated logs older than 14 days (dry run first)
find /var/log/billing-api -name "*.log.*" -mtime +14 -print

What this demonstrates:

rg type and glob filters reduce noise
-l lists files only for bulk replace planning
journalctl piped to rg for structured grep
find -print before -delete safety

Deep Dive

How It Works

grep - Line-oriented regex match; -r recursive (slow on big trees).
ripgrep - Parallel, gitignore-aware, default for code search.
find - Directory traversal by name, time, size, type.
sed - Stream editor for substitute/delete lines.
awk - Column-oriented processing.

Tool Picker

Task	Tool
Code symbol search	`rg pattern src/`
JSON logs	`jq` (preferred) or `rg` on key
File by name	`find . -name '*.py'`
In-place replace	`sed -i.bak` with backup
CSV 3rd column	`awk -F, '{print $3}'`

Python Notes

# Equivalent to rg for one file with line numbers
grep -n "def main" src/app/cli.py
 
# Find empty __init__.py markers
find src -name "__init__.py" -empty

Gotchas

grep -r from / - IO storm and permission errors. Fix: always start from project or /var/log/app.
sed -i without backup on prod - Broken config unrecoverable. Fix: -i.bak or edit locally + deploy.
Regex greediness - Wrong sed matches multiline config. Fix: test on copy; prefer rg locate + manual edit for critical files.
Ignoring binary matches - grep prints "Binary file matches". Fix: rg or grep -I.
Locale breaks character classes - Unexpected sort/match. Fix: LC_ALL=C for ASCII logs.
Awk on JSON - Fragile vs nested objects. Fix: jq for JSON logs.

Alternatives

Alternative	Use When	Don't Use When
IDE search	Local refactor	SSH-only prod logs
`git grep`	Tracked files only	Generated or log files
`ag` / `ack`	Legacy environments	`rg` available
Python script	Complex parsing	One-liner faster in shell

FAQs

rg or git grep?

rg for speed and ignore rules; git grep when searching only committed snapshots at specific revision.

Case insensitive search?

rg -i pattern or grep -i.

Multiline regex?

rg -U multiline mode for cross-line patterns - use sparingly.

find mtime vs atime?

mtime file content change; atime access (often disabled on servers for performance).

sed GNU vs BSD on Mac?

macOS sed requires backup extension sed -i '' - test on target OS.

Exclude venv from grep?

rg auto-ignores; for grep use --exclude-dir=.venv.

Count matches?

rg -c pattern per file or rg pattern | wc -l.

Search compressed logs?

zgrep / zcat file.gz | rg pattern.

Parallel find delete?

Avoid find -delete at scale without -print dry run first.

Regex in Python vs shell?

Prefer Python re in application code; shell regex for operator one-offs only.

re - Regular Expressions - Python regex
Pipes & Text Processing - composing tools
Parsing Logs and Text - log pipelines
Shell Productivity - aliases for search

Stack versions: This page was written for Python 3.14.0 (stable 3.14, maintenance 3.13), FastAPI 0.115+, Django 5.2, Flask 3.1, Pydantic 2, PyTorch 2.6+, pandas 2.2+, Polars 1.x, ruff 0.9+, and uv 0.6+.

Search & Regex

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Search & Regex