Shell flow control statements for

　　for syntax:

for variables in the parameter list 
do 
    command 
done 

or 
for variables in the parameter list; do 
    command 
done

　　Process Control Charts for statement:

　　Example:

[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

　　Parameter list can be more complicated, some need to escape special characters

[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

　　May also be read from the parameter list of variables, a plurality of variables may be

[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

　　Parameter list can also be a value from the command

[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