Engineering Craft › Developer Tooling

grep / ripgrep

Searching text across files from the terminal.

Also known as: grep, ripgrep, rg, find text in files

grep searches for text inside files, and ripgrep (command rg) is a faster, friendlier alternative. They’re how you find where something is used across a codebase, or look through logs.

grep "TODO" notes.txt                    # lines containing TODO
grep -rn "send_email" src/               # search a folder recursively, show line numbers
grep -i "error" app.log                  # ignore case
grep -v "debug" app.log                  # lines that do NOT match
grep -E "ERROR|WARN" app.log             # extended regex: either word
grep -c "timeout" app.log                # just count the matching lines
grep -rn --include="*.py" "db.query" .   # only Python files

rg "send_email"                          # ripgrep: recursive by default
rg -n "TODO" -g "*.ts"                   # only TypeScript files
rg -w "id"                               # match whole words only
rg -C 3 "ValueError"                     # show 3 lines of context around each match

Why ripgrep

• Fast, and searches the current directory recursively by default.
• Respects .gitignore, so it skips node_modules, build output and hidden files.
• Colored, readable output.

Useful combinations

tail -n 1000 app.log | grep "req_8f3a2c"      # filter a pipe
grep -rl "oldFunction" src/ | xargs sed -i 's/oldFunction/newFunction/g'   # careful!

Pipes are covered in pipes and redirection.

Tips

• Patterns are regular expressions by default, so . and ( are special. Use -F (fixed string) to search literally (regular expressions).
• Quote the pattern so the shell doesn’t interpret it.
• Search for the error message or a unique string from the UI to find the code behind it.
• In an editor, project-wide search does the same with a nicer interface. For finding definitions and usages, prefer go to definition.