grep (Global Regular ExPression) in Linux

General user of grep

[command with stdout] | grep pattern

grep -F [pattern] [file..]

:::info -F disables regular expressions :::

greo -F is equivalent to fgrep

Option	Purpose	Description	Example
`-i`	Case-insensitive search	Matches text regardless of case (e.g., "Hello" = "hello")	`grep -i "error" log.txt`
`-w`	Whole word match	Matches only whole words, not substrings	`grep -w "end" notes.txt`
`-x`	Exact line match	Matches lines that are exactly the same as the pattern	`grep -x "done" checklist.txt`
`-F`	Fixed string match	Treats pattern as a literal string (no regex interpretation)	`grep -F "a+b" file.txt`
`-E`	Extended regex	Enables extended regular expressions (like `egrep`)	`grep -E "cat \\| dog” pets.txt`

Option	Purpose	Description	Example
`-r` / `-R`	Recursive search	Searches all files in a directory and its subdirectories	`grep -r "TODO" ./project`
`-l`	List matching files	Shows only filenames that contain matches	`grep -l "main" *.c`
`-L`	List non-matching files	Shows only filenames that do not contain matches	`grep -L "main" *.c`

Option	Purpose	Description	Example
`-n`	Show line numbers	Displays line numbers alongside matching lines	`grep -n "main" code.c`
`--color=auto`	Highlight matches	Highlights matched text in color (if supported by terminal)	`grep --color=auto "fail" log.txt`
`-c`	Count matches	Shows the number of matching lines per file	`grep -c "success" report.txt`

Option	Purpose	Description	Example
`-A NUM`	Show lines after match	Displays NUM lines after each matching line	`grep -A 2 "error" log.txt`
`-B NUM`	Show lines before match	Displays NUM lines before each matching line	`grep -B 2 "error" log.txt`
`-C NUM`	Show lines around match	Displays NUM lines before and after each match	`grep -C 3 "error" log.txt`

Option	Purpose	Description	Example
`-v`	Invert match	Shows lines that do not match the pattern	`grep -v "debug" log.txt`
`-e`	Multiple patterns	Allows specifying multiple patterns to match	`grep -e "cat" -e "dog" pets.txt`