ksh getopts function

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本文介绍如何利用getopt工具解析命令行选项。通过示例代码展示了不同类型的选项及其用法，包括必选参数、可选参数及数值参数等，并提供错误处理方式。

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 ;;
    esac
done
shift $(($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/ksh

USAGE="[+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 description
USAGE+="[i:ii]:[ivalue]"                    # -i, --ii with OPTARG
USAGE+="[c:cc]:[cvalue?description of c]"   # -c, --cc with OPTARG and description
USAGE+="[j:jj]:?[jvalue]"                   # -j, --jj with optional OPTARG
USAGE+="[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 description
USAGE+="[f:ff]#[fvalue]"           # -f, --ff with numeric OPTARG
USAGE+="[g:gg]#?[gvalue:=2]"       # -g, --gg with optional numeric OPTARG, default value


ivalue=
cvalue=
jvalue=
dvalue=ddefault
evalue=evalue
fvalue=
gvalue=2

OPTIND=1
while 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 ..." ;;
    esac
done
shift $((OPTIND-1))

#check at least one additional parameter is required.
if [ $# -eq 0 ]; then
    help
    exit 1
fi

#take actions for each parameters
for PARAM in $@; do
    do_action ${PARAM}
done

exit 0