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grep Examples Cheat Sheet

Search text fast with grep patterns, recursion flags, and context options for debugging and log analysis.

What this cheat sheet is for

This grep examples reference helps you complete common developer tasks quickly and avoid repeated trial-and-error when working under deadlines.

  • When you need a reliable command or pattern during debugging and incident response.
  • When you are implementing a feature and want a known-good syntax example immediately.
  • When onboarding teammates and documenting repeatable workflows for daily use.
  • When reviewing pull requests and verifying that command usage follows best practices.
  • Find error lines in large log files.
  • Search recursively for API keys in source code.
  • Filter command output by pattern quickly.

Basic and case-insensitive search

Search one file

grep "ERROR" app.log

Example:

grep -i "timeout" app.log

Count matches

grep -c "WARN" app.log

Example:

grep -n "panic" app.log

Recursive code search

Search all files in current project

grep -R "TODO" .

Example:

grep -R --include="*.js" "useEffect" src

Exclude directories

grep -R --exclude-dir=node_modules "SECRET" .

Example:

grep -R --exclude="*.min.js" "token" web

Context and regex usage

Show lines before and after match

grep -C 2 "Exception" server.log

Example:

grep -A 3 -B 1 "failed" syslog

Extended regex patterns

grep -E "GET|POST|PUT" access.log

Example:

grep -E "[0-9]{3}" codes.txt

Common mistakes / Pitfalls

  • For huge projects, grep -R . without excludes can be very slow.
  • Shell may expand patterns unexpectedly; quote regex expressions.
  • Binary files can pollute output; use --binary-files=without-match when needed.

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Last updated: February 2026