Go to the previous, next section.

Standards for Command Line Interfaces

Please don't make the behavior of a utility depend on the name used to invoke it. It is useful sometimes to make a link to a utility with a different name, and that should not change what it does.

Instead, use a run time option or a compilation switch or both to select among the alternate behaviors.

Likewise, please don't make the behavior of the program depend on the type of output device it is used with. Device independence is an important principle of the system's design; do not compromise it merely to save someone from typing an option now and then.

If you think one behavior is most useful when the output is to a terminal, and another is most useful when the output is a file or a pipe, then it is usually best to make the default behavior the one that is useful with output to a terminal, and have an option for the other behavior.

Compatibility requires certain programs to depend on the type of output device. It would be disastrous if ls or sh did not do so in the way all users expect. In some of these cases, we supplement the program with a preferred alternate version that does not depend on the output device type. For example, we provide a dir program much like ls except that its default output format is always multi-column format.

It is a good idea to follow the POSIX guidelines for the command-line options of a program. The easiest way to do this is to use getopt to parse them. Note that the GNU version of getopt will normally permit options anywhere among the arguments unless the special argument `--' is used. This is not what POSIX specifies; it is a GNU extension.

Please define long-named options that are equivalent to the single-letter Unix-style options. We hope to make GNU more user friendly this way. This is easy to do with the GNU function getopt_long.

One of the advantages of long-named options is that they can be consistent from program to program. For example, users should be able to expect the "verbose" option of any GNU program which has one, to be spelled precisely `--verbose'. To achieve this uniformity, look at the table of common long-option names when you choose the option names for your program. The table appears below.

If you use names not already in the table, please send `gnu@prep.ai.mit.edu' a list of them, with their meanings, so we can update the table.

It is usually a good idea for file names given as ordinary arguments to be input files only; any output files would be specified using options (preferably `-o'). Even if you allow an output file name as an ordinary argument for compatibility, try to provide a suitable option as well. This will lead to more consistency among GNU utilities, so that there are fewer idiosyncracies for users to remember.

Programs should support an option `--version' which prints the program's version number on standard output and exits successfully, and an option `--help' which prints option usage information on standard output and exits successfully. These options should inhibit the normal function of the command; they should do nothing except print the requested information.

`auto-check'

`-a' in recode.

`auto-reference'

`-A' in ptx.

`after-date'

`-N' in tar.

`all'

`-a' in du, ls, nm, stty, uname, and unexpand.

`all-text'

`-a' in diff.

`almost-all'

`-A' in ls.

`append'

`-a' in etags, tee, time; `-r' in tar.

`archive'

`-a' in cp.

`arglength'

`-l' in m4.

`ascii'

`-a' in diff.

`assume-new'

`-W' in Make.

`assume-old'

`-o' in Make.

`backward-search'

`-B' in etags.

`batch'

Used in GDB.

`baud'

Used in GDB.

`before'

`-b' in tac.

`binary'

`-b' in cpio and diff.

`block-size'

Used in cpio and tar.

`blocks'

`-b' in head and tail.

`break-file'

`-b' in ptx.

`brief'

Used in various programs to make output shorter.

`bytes'

`-c' in head, split, and tail.

`c++'

`-C' in etags.

`catenate'

`-A' in tar.

`cd'

Used in various programs to specify the directory to use.

`changes'

`-c' in chgrp and chown.

`classify'

`-F' in ls.

`colons'

`-c' in recode.

`command'

`-c' in su; `-x' in GDB.

`compare'

`-d' in tar.

`compress'

`-Z' in tar.

`concatenate'

`-A' in tar.

`confirmation'

`-w' in tar.

`context'

Used in diff.

`copyright'

`-C' in ptx and recode.

`core'

Used in GDB.

`count'

`-q' in who.

`count-links'

`-l' in du.

`create'

Used in tar and cpio.

`cxref'

`-x' in etags.

`date'

`-d' in touch.

`debug'

`-d' in Make and m4; `-t' in Bison.

`define'

`-D' in m4.

`defines'

`-d' in Bison and etags.

`delete'

`-D' in tar.

`dereference'

`-L' in chgrp, chown, cpio, du, ls, and tar.

`dereference-args'

`-D' in du.

`diacritics'

`-d' in recode.

`dictionary-order'

`-d' in look.

`diff'

`-d' in tar.

`digits'

`-n' in csplit.

`directory'

Specify the directory to use, in various programs. In ls, it means to show directories themselves rather than their contents. In rm and ln, it means to not treat links to directories specially.

`discard-all'

`-x' in strip.

`discard-locals'

`-X' in strip.

`diversions'

`-N' in m4.

`dry-run'

`-n' in Make.

`ed'

`-e' in diff.

`elide-empty-files'

`-z' in csplit.

`entire-new-file'

`-N' in diff.

`environment-overrides'

`-e' in Make.

`eof'

`-e' in xargs.

`epoch'

Used in GDB.

`error-limit'

Used in Makeinfo.

`error-output'

`-o' in m4.

`escape'

`-b' in ls.

`exclude-from'

`-X' in tar.

`exec'

Used in GDB.

`exit'

`-x' in xargs.

`expand-tabs'

`-t' in diff.

`expression'

`-e' in sed.

`extern-only'

`-g' in nm.

`extract'

`-i' in cpio; `-x' in tar.

`faces'

`-f' in finger.

`fast'

`-f' in su.

`file'

`-f' in info, Make, mt, and tar; `-n' in sed; `-r' in touch.

`file-prefix'

`-b' in Bison.

`file-type'

`-F' in ls.

`files-from'

`-T' in tar.

`fill-column'

Used in Makeinfo.

`flag-truncation'

`-F' in ptx.

`fixed-output-files'

`-y' in Bison.

`follow'

`-f' in tail.

`footnote-style'

Used in Makeinfo.

`force'

`-f' in cp, ln, mv, and rm.

`format'

Used in ls, time, and ptx.

`forward-search'

`-F' in etags.

`fullname'

Used in GDB.

`gap-size'

`-g' in ptx.

`get'

`-x' in tar.

`graphic'

`-i' in ul.

`graphics'

`-g' in recode.

`group'

`-g' in install.

`gzip'

`-z' in tar.

`hashsize'

`-H' in m4.

`header'

`-h' in objdump and recode

`heading'

`-H' in who.

`help'

Used to ask for brief usage information.

`hide-control-chars'

`-q' in ls.

`idle'

`-u' in who.

`ifdef'

`-D' in diff.

`ignore'

`-I' in ls; `-x' in recode.

`ignore-all-space'

`-w' in diff.

`ignore-backups'

`-B' in ls.

`ignore-blank-lines'

`-B' in diff.

`ignore-case'

`-f' in look and ptx; `-i' in diff.

`ignore-errors'

`-i' in Make.

`ignore-file'

`-i' in ptx.

`ignore-indentation'

`-S' in etags.

`ignore-init-file'

`-f' in Oleo.

`ignore-interrupts'

`-i' in tee.

`ignore-matching-lines'

`-I' in diff.

`ignore-space-change'

`-b' in diff.

`ignore-zeros'

`-i' in tar.

`include'

`-i' in etags; `-I' in m4.

`include-dir'

`-I' in Make.

`incremental'

`-G' in tar.

`info'

`-i', `-l', and `-m' in Finger.

`initial'

`-i' in expand.

`initial-tab'

`-T' in diff.

`inode'

`-i' in ls.

`interactive'

`-i' in cp, ln, mv, rm; `-e' in m4; `-p' in xargs; `-w' in tar.

`jobs'

`-j' in Make.

`just-print'

`-n' in Make.

`keep-going'

`-k' in Make.

`keep-files'

`-k' in csplit.

`kilobytes'

`-k' in du and ls.

`line-bytes'

`-C' in split.

`lines'

Used in split, head, and tail.

`link'

`-l' in cpio.

`list'

`-t' in cpio; `-l' in recode.

`list'

`-t' in tar.

`literal'

`-N' in ls.

`load-average'

`-l' in Make.

`login'

Used in su.

`machine'

No listing of which programs already use this; someone should check to see if any actually do and tell gnu@prep.ai.mit.edu.

`macro-name'

`-M' in ptx.

`mail'

`-m' in hello and uname.

`make-directories'

`-d' in cpio.

`makefile'

`-f' in Make.

`mapped'

Used in GDB.

`max-args'

`-n' in xargs.

`max-chars'

`-n' in xargs.

`max-lines'

`-l' in xargs.

`max-load'

`-l' in Make.

`max-procs'

`-P' in xargs.

`mesg'

`-T' in who.

`message'

`-T' in who.

`minimal'

`-d' in diff.

`mode'

`-m' in install, mkdir, and mkfifo.

`modification-time'

`-m' in tar.

`multi-volume'

`-M' in tar.

`name-prefix'

`-a' in Bison.

`new-file'

`-W' in Make.

`no-builtin-rules'

`-r' in Make.

`no-create'

`-c' in touch.

`no-defines'

`-D' in etags.

`no-dereference'

`-d' in cp.

`no-keep-going'

`-S' in Make.

`no-lines'

`-l' in Bison.

`no-prof'

`-e' in gprof.

`no-sort'

`-p' in nm.

`no-split'

Used in Makeinfo.

`no-static'

`-a' in gprof.

`no-time'

`-E' in gprof.

`no-validate'

Used in Makeinfo.

`no-warn'

Used in various programs to inhibit warnings.

`node'

`-n' in info.

`nodename'

`-n' in uname.

`nonmatching'

`-f' in cpio.

`nstuff'

`-n' in objdump.

`null'

`-0' in xargs.

`number'

`-n' in cat.

`number-nonblank'

`-b' in cat.

`numeric-sort'

`-n' in nm.

`numeric-uid-gid'

`-n' in cpio and ls.

`nx'

Used in GDB.

`old-archive'

`-o' in tar.

`old-file'

`-o' in Make.

`one-file-system'

`-l' in tar, cp, and du.

`only-file'

`-o' in ptx.

`only-prof'

`-f' in gprof.

`only-time'

`-F' in gprof.

`output'

In various programs, specify the output file name.

`override'

`-o' in rm.

`owner'

`-o' in install.

`paginate'

`-l' in diff.

`paragraph-indent'

Used in Makeinfo.

`parents'

`-p' in mkdir and rmdir.

`pass-all'

`-p' in ul.

`pass-through'

`-p' in cpio.

`port'

`-P' in finger.

`portability'

`-c' in cpio and tar.

`prefix-builtins'

`-P' in m4.

`prefix'

`-f' in csplit.

`preserve'

Used in tar and cp.

`preserve-environment'

`-p' in su.

`preserve-modification-time'

`-m' in cpio.

`preserve-order'

`-s' in tar.

`preserve-permissions'

`-p' in tar.

`print'

`-l' in diff.

`print-chars'

`-L' in cmp.

`print-data-base'

`-p' in Make.

`print-directory'

`-w' in Make.

`print-file-name'

`-o' in nm.

`print-symdefs'

`-s' in nm.

`question'

`-q' in Make.

`quiet'

Used in many programs to inhibit the usual output. Note: every program accepting `--quiet' should accept `--silent' as a synonym.

`quote-name'

`-Q' in ls.

`rcs'

`-n' in diff.

`read-full-blocks'

`-B' in tar.

`readnow'

Used in GDB.

`recon'

`-n' in Make.

`record-number'

`-R' in tar.

`recursive'

Used in chgrp, chown, cp, ls, diff, and rm.

`reference-limit'

Used in Makeinfo.

`references'

`-r' in ptx.

`regex'

`-r' in tac.

`release'

`-r' in uname.

`relocation'

`-r' in objdump.

`rename'

`-r' in cpio.

`replace'

`-i' in xargs.

`report-identical-files'

`-s' in diff.

`reset-access-time'

`-a' in cpio.

`reverse'

`-r' in ls and nm.

`reversed-ed'

`-f' in diff.

`right-side-defs'

`-R' in ptx.

`same-order'

`-s' in tar.

`same-permissions'

`-p' in tar.

`save'

`-g' in stty.

`se'

Used in GDB.

`sentence-regexp'

`-S' in ptx.

`separate-dirs'

`-S' in du.

`separator'

`-s' in tac.

`sequence'

Used by recode to chose files or pipes for sequencing passes.

`shell'

`-s' in su.

`show-all'

`-A' in cat.

`show-c-function'

`-p' in diff.

`show-ends'

`-E' in cat.

`show-function-line'

`-F' in diff.

`show-tabs'

`-T' in cat.

`silent'

Used in many programs to inhibit the usual output. Note: every program accepting `--silent' should accept `--quiet' as a synonym.

`size'

`-s' in ls.

`sort'

Used in ls.

`sparse'

`-S' in tar.

`speed-large-files'

`-H' in diff.

`squeeze-blank'

`-s' in cat.

`starting-file'

Used in tar and diff to specify which file within a directory to start processing with.

`stop'

`-S' in Make.

`strict'

`-s' in recode.

`strip'

`-s' in install.

`strip-all'

`-s' in strip.

`strip-debug'

`-S' in strip.

`suffix'

`-S' in cp, ln, mv.

`suffix-format'

`-b' in csplit.

`sum'

`-s' in gprof.

`summarize'

`-s' in du.

`symbolic'

`-s' in ln.

`symbols'

Used in GDB and objdump.

`synclines'

`-s' in m4.

`sysname'

`-s' in uname.

`tabs'

`-t' in expand and unexpand.

`tabsize'

`-T' in ls.

`terminal'

`-T' in tput and ul.

`text'

`-a' in diff.

`time'

Used in ls and touch.

`to-stdout'

`-O' in tar.

`total'

`-c' in du.

`touch'

`-t' in Make, ranlib, and recode.

`trace'

`-t' in m4.

`traditional'

`-t' in hello; `-G' in m4 and ptx.

`tty'

Used in GDB.

`typedefs'

`-t' in etags.

`typedefs-and-c++'

`-T' in etags.

`typeset-mode'

`-t' in ptx.

`uncompress'

`-z' in tar.

`unconditional'

`-u' in cpio.

`undefine'

`-U' in m4.

`undefined-only'

`-u' in nm.

`update'

`-u' in cp, `etags', `mv', `tar'.

`verbose'

Print more information about progress. Many programs support this.

`verify'

`-W' in tar.

`version'

Print the version number.

`version-control'

`-V' in cp, ln, mv.

`vgrind'

`-v' in etags.

`volume'

`-V' in tar.

`what-if'

`-W' in Make.

`width'

`-w' in ls and ptx.

`word-regexp'

`-W' in ptx.

`writable'

`-T' in who.

`zeros'

`-z' in gprof.

Go to the previous, next section.