#!/bin/bash
# A small example program for using the new getopt(1) program.
# This program will only work with bash(1)
# An similar program using the tcsh(1) script language can be found
# as parse.tcsh
# Example input and output (from the bash prompt):
# ./option_test.sh -a par1 'another arg' --c-long 'wow!*\?' -cmore -b " very long "
# Option a
# Option c, no argument
# Option c, argument `more'
# Option b, argument ` very long '
# Remaining arguments:
# --> `par1'
# --> `another arg'
# --> `wow!*\?'
# Note that we use `"$@"' to let each command-line parameter expand to a
# separate word. The quotes around `$@' are essential!
# We need TEMP as the `eval set --' would nuke the return value of getopt.
#-o表示短选项，两个冒号表示该选项有一个可选参数，可选参数必须紧贴选项
#如-carg 而不能是-c arg
#--long表示长选项
#"$@"在上面解释过
# -n:出错时的信息
# -- ：举一个例子比较好理解：
#我们要创建一个名字为 "-f"的目录你会怎么办？
# mkdir -f #不成功，因为-f会被mkdir当作选项来解析，这时就可以使用
# mkdir -- -f 这样-f就不会被作为选项。
TEMP=`getopt -o ab:c:: -l a-long,b-long:,c-long:: -n 'option_test.sh' -- "$@"`
echo "TEMP:{$TEMP}"
if [ $? != 0 ] ; then echo "Terminating..." >&2 ; exit 1 ; fi
# Note the quotes around `$TEMP': they are essential!
#set 会重新排列参数的顺序，也就是改变$1,$2...$n的值，这些值在getopt中重新排列过了
eval set -- "$TEMP" #必须用eval
echo "\$#: $#"
for i in "$@"; do
echo "{$i}"
done
#经过getopt的处理，下面处理具体选项。
while true ; do
case "$1" in
-a|--a-long) echo "Option a" ; shift ;;
-b|--b-long) echo "Option b, argument \`$2'" ; shift 2 ;;
-c|--c-long)
# c has an optional argument. As we are in quoted mode,
# an empty parameter will be generated if its optional
# argument is not found.
case "$2" in
"") echo "Option c, no argument"; shift 2 ;;
*) echo "Option c, argument \`$2'" ; shift 2 ;;
esac ;;
--) shift ; break ;;
*) echo "Internal error!" ; exit 1 ;;
esac
done
echo "Remaining arguments:"
for arg do
echo '--> '"\`$arg'" ;
done
==================================================================================
$ set -- a ' b '
$ echo $#
2
$ a="a ' b '"
$ set -- $a
$ echo $#
4
$ set -- "$a"
$ echo $#
1