Appendix F. Standard Command-Line Options

Over time, there has evolved a loose standard for the meanings of command line option flags. The GNU utilities conform more closely to this "standard" than older Unix utilities.

Traditionally, Unix command-line options consist of a dash, followed by one or more lowercase letters. The GNU utilities added a double-dash, followed by a complete word or compound word.

The two most widely-accepted options are:

• -h

  --help

  Help: Give usage message and exit.

• -v

  --version

  Version: Show program version and exit.

Other common options are:

• -a

  --all

  All: show all information or operate on all arguments.

• -l

  --list

  List: list files or arguments without taking other action.

• -o

  Output filename

• -q

  --quiet

  Quiet: suppress stdout.

• -r

  -R

  --recursive

  Recursive: Operate recursively (down directory tree).

• -v

  --verbose

  Verbose: output additional information to stdout or stderr.

• -z

  --compress

  Compress: apply compression (usually gzip).

However:

• In tar and gawk:

  -f

  --file

  File: filename follows.

• In cp, mv, rm:

  -f

  --force

  Force: force overwrite of target file(s).

Many Unix and Linux utilities deviate from this "standard," so it is dangerous to assume that a given option will behave in a standard way. Always check the man page for the command in question when in doubt.

A complete table of recommended options for the GNU utilities is available at http://www.gnu.org/prep/standards_19.html.