getopt -- external command to parse shell file options

getopt external command to parse shell file options	Command

SYNOPSIS

getopt [-c cmdname] optiondesc argument ...

The getopt command is often used in shell scripts to parse command line options. The first command argument, optiondesc, contains each option letter that is valid in the following command argument strings. An option letter followed by a colon (:) means that the preceding option letter requires a further argument (as in -o file).

getopt considers each argument that begins with a - to be a potential option and prints an error if it does not find the argument in optiondesc. Scanning for further options stops at the first argument which does not begin with - or with an argument that is --. In either case, the options are separated from the rest of the non-option argument strings by a -- string.

The most common construct for using getopt is

set - - $(getopt [-c cmdname] optiondesc "$@")

This may be used inside the MKS KornShell to parse the arguments to a shell script; see sh for more about the shell.

Options

-c cmdname: uses cmdname rather than getopt when displaying error messages.

EXAMPLE

The command:

getopt -c diff befhnmD: -eh -D string file1 file2

which parses the diff command line options, would produce the following output:

-e -h -D string -- file1 file2

The following is a more realistic and complex example of using getopt in a shell script.

# Example illustrating use of getopt command. This
# shell script would implement the paste command,
# using getopt to process options, if the underlying
# functionality was embedded in hypothetical utilities
# hpaste and vpaste, which perform horizontal and
# vertical pasting respectively.
#
paste=vpaste  # default is vertical pasting
seplist="\t"  # default separator is tab

set -- $(getopt -c $0 d:s "$@")
if  [ $? -ne 0 ]
then  print >&2 "Usage: $0 [-s] [-d seplist] file ..."
  exit 1
fi
for o
do case "$o" in
  -d)  shift; seplist="$1"; shift;;
  -s)  paste=hpaste; shift;;
  --)  shift; break;;
  esac
done

# perform actual paste command
$paste -d "$seplist" "$@"