GETOPT(1) User Commands GETOPT(1)

NAME

getopt - parse command options

SYNOPSIS

set -- ` getopt optstring $ * `

DESCRIPTION

The getopts command supersedes getopt. For more information, see
NOTES below.


getopt is used to break up options in command lines for easy parsing
by shell procedures and to check for legal options. optstring is a
string of recognized option letters; see getopt(3C). If a letter is
followed by a colon (:), the option is expected to have an argument
which may or may not be separated from it by white space. The special
option - is used to delimit the end of the options. If it is used
explicitly, getopt recognizes it; otherwise, getopt generates it; in
either case, getopt places it at the end of the options. The
positional parameters ($1 $2 ...) of the shell are reset so that each
option is preceded by a - and is in its own positional parameter;
each option argument is also parsed into its own positional
parameter.

EXAMPLES

Example 1: Processing the arguments for a command

The following code fragment shows how one might process the arguments
for a command that can take the options -a or -b, as well as the
option -o, which requires an argument:


set -- `getopt abo: $*`
if [ $? != 0 ]
then
echo $USAGE
exit 2
fi
for i in $*
do
case $i in
-a | -b) FLAG=$i; shift;;
-o) OARG=$2; shift 2;;
--) shift; break;;
esac
done


This code accepts any of the following as equivalent:


cmd -aoarg filename1 filename2
cmd -a -o arg filename1 filename2
cmd -oarg -a filename1 filename2
cmd -a -oarg -- filename1 filename2

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+---------------+-----------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|CSI | enabled |
+---------------+-----------------+

SEE ALSO

Intro(1), getoptcvt(1), getopts(1), sh(1), shell_builtins(1),
getopt(3C), attributes(7)

DIAGNOSTICS

getopt prints an error message on the standard error when it
encounters an option letter not included in optstring.

NOTES

Reset optind to 1 when rescanning the options.


getopt does not support the part of Rule 8 of the command syntax
standard (see Intro(1)) that permits groups of option-arguments
following an option to be separated by white space and quoted. For
example,

cmd -a -b -o "xxx z yy" filename


is not handled correctly. To correct this deficiency, use the getopts
command in place of getopt.


If an option that takes an option-argument is followed by a value
that is the same as one of the options listed in optstring (referring
to the earlier EXAMPLES section, but using the following command
line:

cmd -o -a filename


getopt always treats it as an option-argument to -o; it never
recognizes -a as an option. For this case, the for loop in the
example shifts past the filename argument.

June 1, 2022 GETOPT(1)