转:http://blog.sina.com.cn/s/blog_6151984a0100ekqj.html
for in 格式
for 无$变量 in 字符串 do $变量 done |
一简单的字符串 枚举遍历法,利用for in格式对字符串按空格切份的功能 SERVICES="80 22 25 110 8000 23 20 21 3306 " for x in $SERVICES do iptables -A INPUT -p tcp --dport $x -m state --state NEW -j ACCEPT done |
for variable in values --------字符串数组依次赋值
#!/bin/sh for i in a b c 字符串列表A B C 字符串用空格分隔,没有括号,没有逗号, 然后循环将其依次赋给变量i 变量没有$ do echo "i is $i" done |
[macg@machome ~]$ sh test.sh i is a i is b i is c |
for in 里,变量和*不等价
#!/bin/bash for i in *.h ; do cat ${i}.h done |
[macg@vm test]$ ./tip.sh cat: *.h.h: No such file or directory $i代表的是整个路径,而不是*.h里的.h前面的部分 |
改正
#!/bin/bash for i in *.h do cat $i done |
[macg@vm test]$ echo hahaha >>1.h [macg@vm test]$ echo ha >>2.h [macg@vm test]$ ./tip.sh hahaha ha |
例2:
for i in /etc/profile.d/*.sh do $i done |
$i代表的是/etc/profile.d/color.sh, /etc/profile.d/alias.sh, /etc/profile.d/default.sh |
for in 对(命令行,函数)参数遍历
test() { local i for i in $* ; do echo "i is $i" done } $*是字符串:以"参数1 参数2 ... " 形式保存所有参数 $i是变量i的应用表示 |
[macg@machome ~]$ sh test.sh p1 p2 p3 p4 i is p1 i is p2 i is p3 i is p4 |
for in语句与通配符*合用,批量处理文件
批量改文件名
[root@vm testtip]# ls aaa.txt ccc.txt eee.txt ggg.txt hhh.txt jjj.txt lll.txt nnn.txt bbb.txt ddd.txt fff.txt go.sh iii.txt kkk.txt mmm.txt ooo.txt |
[root@vm testtip]# cat go.sh for i in *.txt *.txt相当于一个字符串数组,依次循环赋值给i do mv "$i" "$i.bak" done |
[root@vm testtip]# sh go.sh [root@vm testtip]# ls aaa.txt.bak ccc.txt.bak eee.txt.bak ggg.txt.bak hhh.txt.bak jjj.txt.bak lll.txt.bak nnn.txt.bak bbb.txt.bak ddd.txt.bak fff.txt.bak go.sh iii.txt.bak kkk.txt.bak mmm.txt.bak ooo.txt.bak |
for in语句与` `和$( )合用,利用` `或$( )的将多行合为一行的缺陷,实际是合为一个字符串数组
for i in $(ls *.txt) do echo $i done |
[macg@machome ~]$ sh test 111-tmp.txt 111.txt 22.txt 33.txt |
或者说,利用for in克服` `和$( ) 的多行合为一行的缺陷
利用for in 自动对字符串按空格遍历的特性,对多个目录遍历
LIST="rootfs usr data data2" for d in $LIST; do mount /backup/$d rsync -ax --exclude fstab --delete /$d/ /backup/$d/ umount /backup/$d done |