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(Or "option", "flag", "switch", "option switch") Anargument to a command that modifies its function rather thanproviding data. Options generally start with "-" in Unix or"/" in MS-DOS. This is usually followed by a single letteror occasionally a digit. More recently, GNU softwareadopted the --longoptionname style, usually in addition totraditional, single-character, -x style equivalents.Some commands require each option to be a separate argument,introduced by a new "-" or "/", others allow multiple optionletters to be concatenated into a single argument with asingle "-" or "/", e.g. "ls -al". A few Unix commands(e.g. ar, tar) allow the "-" to be omitted. Some optionsmay or must be followed by a value, e.g. "cc prog.c -o prog",sometimes with and sometimes without an intervening space.getopt and getopts are commands for parsing command lineoptions. There is also a C library routine called getoptfor the same purpose.