grep and ripgrep for code search: recursion, filters and exit codes

What it is

grep prints the lines of its input that match a pattern. The GNU grep manual documents -r for recursive search, --include=glob and --exclude-dir=glob to restrict which files and directories are read, -F for fixed strings, -E for extended regular expressions, -P for Perl-compatible ones, -w for whole words, -l for file names only, -c for counts, -n for line numbers and -C num for context lines. The exit status is 0 if a line was selected, 1 if none was, and 2 if an error occurred.

ripgrep (rg) is a separate tool with a similar interface. Its guide describes "automatic filtering": when given a directory it skips files matching .gitignore, .ignore and .rgignore globs, hidden files and directories, and binary files (any file containing a NUL byte), and it does not follow symlinks. -u, -uu and -uuu progressively switch those filters off; --no-ignore, --hidden, --text and --follow do so individually. -g '*.rs' and -t rust restrict by glob or file type, and --files lists what would be searched.

Why it matters

An empty result means different things in the two tools. grep may have searched build output and vendored dependencies and buried the hit; ripgrep may have skipped the wanted file because it is git-ignored or hidden. Scripts and agents that branch on "no matches" must know which case they are in, and must treat exit status 2 as "the search failed", not as "not found".

How to apply

• Search literal strings with -F in both tools and quote the pattern; use regular expressions only when needed.
• Restrict scope explicitly: grep -rn --include='*.py' --exclude-dir=.venv pattern . or rg -n -t py pattern.
• When ripgrep finds nothing, retry with -uu before concluding the text is absent; rg --files shows the searched set.
• Feed file lists to other tools with -l; add -Z (grep) or -0 (ripgrep) together with xargs -0 when names may contain spaces.
• Use ripgrep's -S (smart case), -C 3 for context, -U for multi-line patterns and --sort path when output order must be stable; the guide notes that sorting disables parallelism.

Pitfalls

The grep manual states that range expressions such as [a-z] are unspecified outside the C locale; use [[:lower:]] or run with LC_ALL=C. -P is a GNU extension that other grep implementations may lack. By default grep stops printing from a file once it sees NUL bytes and reports a binary-file match; -a forces text. ripgrep stops searching a file reached by directory traversal at the first NUL byte; --binary keeps searching it without printing binary content, -a treats it as text. ripgrep's output order varies between runs unless --sort is used.