用途说明
在shell中用于循环。类似于其他编程语言中的for，但又有些不同。for循环是Bash中最常用的语法结构。
常用格式
格式一
for 变量
do
语句
done
格式二
for 变量 in 列表
do
语句
done
格式三
for ((变量=初始值; 条件判断; 变量变化))
do
语句
done
使用示例
for的无限循环
#!/bin/bashfor (( ; ; ))
do echo "infinite loops [ hit CTRL+C to stop]"
done |
示例一
- for s in ac apropos at arp
- do
- echo $s
- done
[root@jfht ~]# for s in ac apropos at arp
> do
> echo $s
> done
ac
apropos
at
arp
[root@jfht ~]#
示例二
- for f in *
- do
- echo $f
- done
[root@jfht ~]# for f in *
> do
> echo $f
> done
anaconda-ks.cfg
bak181
hlx
install.log
install.log.syslog
job.sh
job.txt
mbox
mini
setup
temp
vsftpd-2.0.5-16.el5.i386.rpm
vsftpd.conf
work191
[root@jfht ~]#
示例三
- ls >ls.txt
- for s in $(cat ls.txt)
- do
- echo $s
- done
[root@jfht ~]# ls >ls.txt
[root@jfht ~]# for s in $(cat ls.txt)
>
> do
>
> echo $s
>
> done
anaconda-ks.cfg
bak181
hlx
install.log
install.log.syslog
job.sh
job.txt
ls.txt
mbox
mini
setup
temp
vsftpd-2.0.5-16.el5.i386.rpm
vsftpd.conf
work191
[root@jfht ~]#
示例四
- print_args()
- {
- for arg in "$@"
- do
- echo $arg
- done
- }
- print_args 1 2 3 4
- print_args "this is a test"
- "color: #000000;">print_args this is a test
[root@smsgw root]# print_args()
> {
> for arg in "$@"
> do
> echo $arg
> done
> }
[root@smsgw root]# print_args 1 2 3 4
1
2
3
4
[root@smsgw root]# print_args "this is a test"
this is a test
[root@smsgw root]# print_args this is a test
this
is
a
test
示例五
- for ((i=0; i<</span>10; ++i))
- do
- echo $i
- done
[root@smsgw root]# for ((i=0; i<10; ++i))
> do
> echo $i
> done
0
1
2
3
4
5
6
7
8
9
示例六 列表为数组
- AREAS=(1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913)
- NAMES=(南京 无锡 徐州 常州 苏州 南通 连云港 淮安 盐城 扬州 镇江 泰州 宿迁)
- NUM_OF_AREAS=13
- area_name_of()
- {
- for ((I=0; I<$NUM_OF_AREAS; ++I))
- do
- if [ "$1" == "${AREAS[I]}" ]; then
- echo "${NAMES[I]}"
- fi
- done
- }
- echo $(area_name_of 1903)
- for AREA in ${AREAS[*]};
- do
- echo $AREA $(area_name_of $AREA)
- done
[root@smsgw root]# AREAS=(1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913)
[root@smsgw root]# NAMES=(南京 无锡 徐州 常州 苏州 南通 连云港 淮安 盐城 扬州 镇江 泰州 宿迁)
[root@smsgw root]# NUM_OF_AREAS=13
[root@smsgw root]# area_name_of()
> {
> for ((I=0; I<$NUM_OF_AREAS; ++I))
> do
> if [ "$1" == "${AREAS[I]}" ]; then
> echo "${NAMES[I]}"
> fi
> done
> }
[root@smsgw root]# echo $(area_name_of 1903)
徐州
[root@smsgw root]# for AREA in ${AREAS[*]};
> do
> echo $AREA $(area_name_of $AREA)
> done
1901 南京
1902 无锡
1903 徐州
1904 常州
1905 苏州
1906 南通
1907 连云港
1908 淮安
1909 盐城
1910 扬州
1911 镇江
1912 泰州
1913 宿迁
[root@smsgw root]#
示例七 bash version 3.0+
- bash --version
- for i in {1..5}
- do
- echo "Welcome $i times"
- done
[root@smsgw root]# bash --version
GNU bash, version 2.05b.0(1)-release (i386-redhat-linux-gnu)
Copyright (C) 2002 Free Software Foundation, Inc.
[root@smsgw root]# for i in {1..5}
> do
> echo "Welcome $i times"
> done
Welcome {1..5} times
[root@smsgw root]#
换个较高版本的Linux。
[root@jfht ~]# bash --version
GNU bash, version 3.2.25(1)-release (i686-redhat-linux-gnu)
Copyright (C) 2005 Free Software Foundation, Inc.
[root@jfht ~]# for i in {1..5}
> do
> echo "Welcome $i times"
> done
Welcome 1 times
Welcome 2 times
Welcome 3 times
Welcome 4 times
Welcome 5 times
[root@jfht ~]#
示例八 Bash v4.0+
- echo "Bash version ${BASH_VERSION}..."
- for i in {0..10..2}
- do
- echo "Welcome $i times"
- done
[root@smsgw root]# echo "Bash version ${BASH_VERSION}..."
Bash version 2.05b.0(1)-release...
[root@smsgw root]# for i in {0..10..2}
> do
> echo "Welcome $i times"
> done
Welcome {0..10..2} times
[root@smsgw root]#
换个较高版本的Linux。
[root@jfht ~]# echo "Bash version ${BASH_VERSION}..."
Bash version 3.2.25(1)-release...
[root@jfht ~]# for i in {0..10..2}
> do
> echo "Welcome $i times"
> done
Welcome {0..10..2} times
[root@jfht ~]#
传说Bash4.0可以支持这种语法。
Bash version 4.0.33(0)-release...
Welcome 0 times
Welcome 2 times
Welcome 4 times
Welcome 6 times
Welcome 8 times
Welcome 10 times