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