Linux命令之for - Bash中的For循环_linux bash for-优快云博客

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本文链接：http://codingstandards.iteye.com/blog/778999 （转载请注明出处）

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

语句

done

格式二

for 变量 in 列表

语句

done

格式三

for ((变量=初始值; 条件判断; 变量变化))

语句

done

使用示例

示例一

Bash代码

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

Bash代码

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

Bash代码

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

Bash代码

print_args()
{
for arg in "$@"
do
echo $arg
done
}
print_args 1 2 3 4
print_args "this is a test"
<span style="color: #000000;">print_args this is a test</span>

[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

Bash代码

for ((i=0; i<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

Bash代码

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+

Java代码

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+

Bash代码

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