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25.1.1 Program Argument Syntax Conventions

POSIX recommends these conventions for command line arguments. getopt (see Getopt) and argp_parse (see Argp) make it easy to implement them.

GNU adds long options to these conventions. Long options consist of ‘--’ followed by a name made of alphanumeric characters and dashes. Option names are typically one to three words long, with hyphens to separate words. Users can abbreviate the option names as long as the abbreviations are unique.

To specify an argument for a long option, write ‘--name=value’. This syntax enables a long option to accept an argument that is itself optional.

Eventually, GNU systems will provide completion for long option names in the shell.