fgrep

View documentation for the original command

$ tldr grep

fgrep [options] PATTERN [FILE…]

-i, --ignore-case
    Ignore case distinctions in patterns and data

-v, --invert-match
    Select non-matching lines

-n, --line-number
    Prefix each line with its line number

-l, --files-with-matches
    Output only names of files containing matches

-c, --count
    Suppress normal output; show count of matching lines per file

-w, --word-regexp
    Match only whole words (selects lines with exact word matches)

-x, --line-regexp
    Select only matches that exactly match entire lines

-f FILE, --file=FILE
    Read patterns from FILE (one per line)

-h, --no-filename
    Suppress filename prefix on output

-q, --quiet, --silent
    Suppress all output; exit status indicates match

fgrep, short for "fixed grep", is a utility for searching files for literal strings rather than regular expressions. Unlike grep (which interprets patterns as basic regex) or egrep (extended regex), fgrep treats all patterns as fixed strings, enabling faster searches on large files or datasets without regex parsing overhead.

It reads patterns from the command line or a file and scans input files (or stdin) line-by-line, printing matching lines by default. Ideal for searching configuration files, logs, or code for exact terms like error messages, keywords, or identifiers.

Key advantages include speed on non-regex patterns and simplicity for literal matches. Output includes the filename (unless suppressed) and line content. Common in scripts for batch processing. On modern GNU systems, fgrep is typically a symlink to grep with the -F flag implied, ensuring POSIX compatibility while leveraging grep's enhancements.

Deprecated on some systems; use grep -F for portability. Does not support regex metacharacters as literals unless escaped. Multiple patterns separated by newlines or pipes treated as alternatives.

0: Matches found
1: No matches
2: Error

fgrep 'error' *.log
fgrep -i -l 'TODO' src/*.c
fgrep -f patterns.txt largefile

Introduced in early Unix Version 7 (1979) alongside grep and egrep for optimized literal searches. Maintained in POSIX standards for compatibility. In GNU coreutils since 1987, fgrep links to grep with fixed-string mode.

grep(1), egrep(1), zgrep(1), sed(1)