奇怪的shell调试输出

greegree

这个是shell的源文件：

#!/bin/sh -x # #    test for umount # #    ./mount $(ls /dev/discs/disc0/) # echo -e "\r\n#\r\n# $# \r\n# $* \r\n#" while [ 1 ] do     DISK=$(mount | tail -n 1 | grep 'tmp' | awk '{print $3}')     if [ -n "$DISK" ];then         echo -e "\r\n#\r\n# umount DISK=$DISK \r\n#"         umount $DISK         [ $? == 0 ] && rm -rf $DISK     else         break     fi done

以下是调试的输出信息:

+ echo -e \r\n#\r\n# 0 \r\n# \r\n# # # 0 # # + [ 1 ] + mount + tail -n 1 + grep tmp + awk {print $3} + echo -e \r\n#\r\n# 0 \r\n# \r\n# # # 0 # # + [ 1 ] + mount + tail -n 1 + grep tmp + awk {print $3} + DISK=/etc/tmp/disc + [ -n /etc/tmp/disc ] + echo -e \r\n#\r\n# umount DISK=/etc/tmp/disc \r\n# # # umount DISK=/etc/tmp/disc # + umount /etc/tmp/disc + DISK=/etc/tmp/disc + [ -n /etc/tmp/disc ] + echo -e \r\n#\r\n# umount DISK=/etc/tmp/disc \r\n# # # umount DISK=/etc/tmp/disc # + umount /etc/tmp/disc + + [[ 0 0 == == 0 0 ] ] + + rmrm -rf -rf /etc/tmp/disc /etc/tmp/disc + + [[ 1 1 ] ] + + mountmount + + tailtail -n -n 1 1 + + grepgrep tmp tmp + + awkawk {print $3} {print $3} + + DISK=DISK= + + [[ -n -n ] ] + + breakbreak

为啥会有两个加号的输出呢？
实际上循环只执行了一遍呀

爱知

if 语句里面的 if 语句

waker

$()命令替代会发起subshell

greegree

原帖由 waker 于 2008-8-18 14:28 发表
$()命令替代会发起subshell

多谢！！