2. Invoking grep

grep comes with a rich set of options from POSIX.2 and GNU extensions.

`-c'

`--count'

Suppress normal output; instead print a count of matching lines for each input file. With the `-v', `--invert-match' option, count non-matching lines.

`-e pattern'

`--regexp=pattern'

Use pattern as the pattern; useful to protect patterns beginning with a `-'.

`-f file'

`--file=file'

Obtain patterns from file, one per line. The empty file contains zero patterns, and therefore matches nothing.

`-i'

`--ignore-case'

Ignore case distinctions in both the pattern and the input files.

`-l'

`--files-with-matches'

Suppress normal output; instead print the name of each input file from which output would normally have been printed. The scanning of every file will stop on the first match.

`-n'

`--line-number'

Prefix each line of output with the line number within its input file.

`-o'

`--only-matching'

Print only the part of matching lines that actually matches pattern.

`-q'

`--quiet'

`--silent'

Quiet; do not write anything to standard output. Exit immediately with zero status if any match is found, even if an error was detected. Also see the `-s' or `--no-messages' option.

`-s'

`--no-messages'

Suppress error messages about nonexistent or unreadable files. Portability note: unlike GNU grep, traditional grep did not conform to POSIX.2, because traditional grep lacked a `-q' option and its `-s' option behaved like GNU grep's `-q' option. Shell scripts intended to be portable to traditional grep should avoid both `-q' and `-s' and should redirect output to `/dev/null' instead.

`-v'

`--invert-match'

Invert the sense of matching, to select non-matching lines.

`-x'

`--line-regexp'

Select only those matches that exactly match the whole line.