Appendix F. Command-Line Options

Many executables, whether binaries or script files, accept options to modify their run-time behavior. For example: from the command line, typing command -o would invoke command, with option o.

F.1. 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:

Other common options are:



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