Glossary

An argument to a command that modifies its function rather than providing data. Options generally start with "-" in UNIX or "/" in MS-DOS. This is usually followed by a single letter or occasionally a digit.Some commands require each option to be a separate argument, introduced by a new "-" or "/", others allow multiple option letters to be concatenated into a single argument with a single "-" or "/", e.g. "ls -al". A few UNIX commands (such as ar and tar) allow the "-" to be omitted. Some options may or must be followed by a value (for example, "cc prog.c -o prog"), sometimes with and sometimes without an intervening space.