Master Linux grep: Essential Options and Real‑World Examples

The grep command is a powerful text‑search utility on Linux that supports regular expressions to locate matching lines in files.

Basic syntax

grep [options] [pattern] [files]

Common options

-a, --text

: Treat binary files as text. -c, --count: Show only the number of matching lines. -e pattern, --regexp=pattern: Specify a pattern; multiple patterns are allowed. -f file, --file=file: Read patterns from a file, one per line. -i, --ignore-case: Ignore case distinctions. -l, --files-with-matches: Print only the names of files with matches. -n, --line-number: Prefix each matching line with its line number. -r, --recursive: Recursively search sub‑directories. -v, --invert-match: Output lines that do **not** match. -x, --line-regexp: Match only whole lines. -w, --word-regexp: Match whole words only.

Practical examples

Search for a specific string:

grep "hello" file.txt
grep "hello" folder/file.txt

Search for multiple strings (OR logic): grep -E "hello|world" file.txt Ignore case: grep -i "hello" file.txt Show line numbers: grep -n "hello" file.txt Invert match (show non‑matching lines): grep -v "hello" file.txt Search a range of context lines (2 lines after match):

grep -A 2 "hello" file.txt   # after
grep -B 2 "hello" file.txt   # before
grep -C 2 "hello" file.txt   # both

Search whole words only: grep -w "hello" file.txt Count occurrences: grep -c "hello" file.txt Search specific file types:

grep "hello" *.txt
grep "hello" --include "*.txt" folder/

Search recursively in sub‑directories:

grep -r "hello" folder/
grep -R "hello" folder/

Force search in binary files: grep -a "hello" binary_file.bin Exclude specific directories: grep -r "hello" folder/ --exclude-dir=log/ Limit search to the first N lines:

grep -m 10 "hello" file.txt   # only first 10 lines

Show only the matching part of each line: grep -o "hello" file.txt Display non‑matching lines: grep -L "hello" file.txt Show surrounding context with -C: grep -C 2 "hello" file.txt Search multiple files at once: grep "hello" file1.txt file2.txt file3.txt Ignore surrounding whitespace when matching whole words: grep -w "hello" file.txt View upstream or downstream context:

grep -B 2 "hello" file.txt   # before
grep -A 3 "hello" file.txt   # after

Source: https://www.cnblogs.com/LanTianYou/p/17359397.html