Shell流程控制语句for

for 变量 in 参数列表
do
    命令
done

或者
for 变量 in 参数列表 ; do
    命令
done

[root@youxi1 ~]# vim a.sh
#!/bin/bash
for var in a1 a2 b1 b2
do
 echo $var
done
[root@youxi1 ~]# sh a.sh
a1
a2
b1
b2

[root@youxi1 ~]# vim b.sh
#!/bin/bash
for var in I\'m "hello world" "c1 c2 d1 d2"
do
 echo $var
done
[root@youxi1 ~]# sh b.sh 
I'm
hello world
c1 c2 d1 d2

[root@youxi1 ~]# vim c.sh
#!/bin/bash
list="e1 e2 f1 f2"
list2="hello world"
for var in $list $list2
do
 echo $var
done
[root@youxi1 ~]# sh c.sh 
e1
e2
f1
f2
hello
world

[root@youxi1 ~]# vim d.sh
#!/bin/bash
for var in `head -5 /etc/passwd`
do
 echo $var
done
[root@youxi1 ~]# sh d.sh 
root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/bin:/sbin/nologin
daemon:x:2:2:daemon:/sbin:/sbin/nologin
adm:x:3:4:adm:/var/adm:/sbin/nologin
lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin

for ((变量赋值;条件判断;一次循环完成后执行的操作))
do
    命令
done

[root@youxi1 ~]# vim a.sh 
#!/bin/bash
i=0
for ((;i<=10;)) ; do
 echo "Num is $i"
 let i++
done
[root@youxi1 ~]# sh a.sh  
Num is 0
Num is 1
Num is 2
Num is 3
Num is 4
Num is 5
Num is 6
Num is 7
Num is 8
Num is 9
Num is 10

[root@youxi1 ~]# vim a.sh 
#!/bin/bash
for ((a=0,b=5;a<=10;a++,b--)) ; do
 echo "a-b="$[a-b]
done
[root@youxi1 ~]# sh a.sh  
a-b=-5
a-b=-3
a-b=-1
a-b=1
a-b=3
a-b=5
a-b=7
a-b=9
a-b=11
a-b=13
a-b=15

[root@youxi1 ~]# vim a.sh
#!/bin/bash
for i in `seq -5 5` ; do
 echo $i
done
[root@youxi1 ~]# sh a.sh 
-5
-4
-3
-2
-1
0
1
2
3
4
5