Are there standards for Linux command line switches and arguments?

Question

This is more about the invocation of a program, than any language or parser (though I\'m sure choice of parser library can depend on this). See, I\'ve used a lot of Linux co

Answer 1

A quick summary of the thread:

• You CLI should display help when missing or incorrect parameters in addition to the error message if any.

• You should use - for a single letter flag or option and -- for a long option, for instance -a and --all

• All programs should support two standard options: -v --version and -h --help.

  • -h and --help => Give usage message and exit
  • -v and --version => Show program version and exit

See the links (IEEE and GNU getopt) provided on this answer https://stackoverflow.com/a/8957246

Answer 2

ESR has collected a lot of information about this in his book "The Art of UNIX Programming". Here's a snippet.

-a
All (without argument). If there is a GNU-style --all option, for -a to be anything but a synonym for it would be quite surprising. Examples: fuser(1), fetchmail(1).

Append, as in tar(1). This is often paired with -d for delete.

-b
Buffer or block size (with argument). Set a critical buffer size, or (in a program having to do with archiving or managing storage media) set a block size. Examples: du(1), df(1), tar(1).

Batch. If the program is naturally interactive, -b may be used to suppress prompts or set other options appropriate to accepting input from a file rather than a human operator. Example: flex(1).

-c
Command (with argument). If the program is an interpreter that normally takes commands from standard input, it is expected that the option of a -c argument will be passed to it as a single line of input. This convention is particularly strong for shells and shell-like interpreters. Examples: sh(1), ash(1), bsh(1), ksh(1), python(1). Compare -e below.

Check (without argument). Check the correctness of the file argument(s) to the command, but don't actually perform normal processing. Frequently used as a syntax-check option by programs that do interpretation of command files. Examples: getty(1), perl(1).

See the full list at http://catb.org/~esr/writings/taoup/html/ch10s05.html

Answer 3

Generally, yes.

• IEEE
• GNU getopt

Answer 4

The Linux/GNU command line interface follows the POSIX standard. This is noted by GNU in their standards: http://www.gnu.org/prep/standards/html_node/Command_002dLine-Interfaces.html.

Command line syntax is also part of the Single Unix Specification, though --long-options are a GNU innovation IIRC.

See here: http://pubs.opengroup.org/onlinepubs/7908799/xbd/utilconv.html

But yes, this standard is implemented as getopt.