ksh getopts function

This is a sample on how to use getopts to parse command line options.

Principle

while getopts "ab:c" opt; do    case $opt in        a  ) process option -a ;;        b  ) process option -b             $OPTARG is the option's argument ;;        c  ) process option -c ;;        \? ) print 'usage: bob [-a] [-b barg] [-c] args ...'             exit 1 ;;    esacdoneshift $(($OPTIND - 1))normal processing of arguments ...

• If a letter is followed by a ':', the option requires an argument.
• If a letter is followed by a '#', the option requires a numeric argument.
• The ':' or '#' may be followed by [description], i.e., a descriptive string enclosed in square brackets that is used when generating usage error messages.
• The leading ':',if the user types an invalid option, getopts normally prints an error message (of the form cmd: -o: unknown option) and sets opt to ?. getopts finishes processing all its options, and if an error was encountered, the shell exits. However -- now here's an obscure kludge -- if you begin the option letter string with a colon, getopts won't print the message, and shell will not exit. This allows you to handle error messages on your own.

  while getopts ":ab:c" opt; do

Code Description

#!/bin/kshUSAGE="[+NAME?$0]"USAGE+="[+DESCRIPTION?this is program description]"     # this two lines are used for unix man page style section headings           USAGE+="[a:aa]"                             # -a, --aa                                                   USAGE+="[b:bb?description of b]"            # -b, --bb with descriptionUSAGE+="[i:ii]:[ivalue]"                    # -i, --ii with OPTARGUSAGE+="[c:cc]:[cvalue?description of c]"   # -c, --cc with OPTARG and descriptionUSAGE+="[j:jj]:?[jvalue]"                   # -j, --jj with optional OPTARGUSAGE+="[d:dd]:?[dvalue:=ddefault]"         # -d, --dd with optional OPTARG, default value USAGE+="[e:ee]:?[evalue:=edefault?description of e]"    # -e, --ee with optional OPTARG, default value, and descriptionUSAGE+="[f:ff]#[fvalue]"           # -f, --ff with numeric OPTARGUSAGE+="[g:gg]#?[gvalue:=2]"       # -g, --gg with optional numeric OPTARG, default valueivalue=cvalue=jvalue=dvalue=ddefaultevalue=evaluefvalue=gvalue=2OPTIND=1while getopts "$USAGE" opt; do    case $opt in        a) echo "in a, OPTARG=${OPTARG}" ;;        b) echo "in b, OPTARG=${OPTARG}" ;;        i) echo "in i, OPTARG=${OPTARG}" ;;        c) echo "in c, OPTARG=${OPTARG}" ;;        j) echo "in j, OPTARG=${OPTARG}" ;;        d) echo "in d, OPTARG=${OPTARG}" ;;        e) echo "in e, OPTARG=${OPTARG}" ;;        f) echo "in f, OPTARG=${OPTARG}" ;;        g) echo "in g, OPTARG=${OPTARG}" ;;           \?) echo "Unknow Option ..." ;;    esacdoneshift $((OPTIND-1))#check at least one additional parameter is required.if [ $# -eq 0 ]; then    help    exit 1fi#take actions for each parametersfor PARAM in $@; do    do_action ${PARAM}doneexit 0

Usage Output

Input an invalid option

$ ./t.ksh -n

./t.ksh: -n: unknown option

Unknow Option ...

Usage: ./t.ksh [-ab] [-i ivalue] [-c cvalue] [-j[jvalue]] [-d[dvalue]] [-e[evalue]] [-f fvalue] [-g[gvalue]]

Show help information

$ ./t.ksh -?

Usage: ./t.ksh [-ab] [-i ivalue] [-c cvalue] [-j[jvalue]] [-d[dvalue]] [-e[evalue]] [-f fvalue] [-g[gvalue]]

Show long-description help information

$ ./t.ksh --help

Usage: ./t.ksh [ options ]

OPTIONS

  -a, --aa

  -b, --bb        description of b

  -i, --ii=ivalue

  -c, --cc=cvalue description of c

  -j, --jj[=jvalue] The option value may be omitted.

  -d, --dd[=dvalue] The option value may be omitted. The default value is ddefault.

  -e, --ee[=evalue]

                  description of e The option value may be omitted. The default value is edefault.

  -f, --ff=fvalue

  -g, --gg[=gvalue] The option value may be omitted. The default value is 2.