Shell--for in Loop __shell

For in format
For no $variable in string
Do
$variable
Done
A simple string enumeration calendar, using for in format to cut strings by spaces
SERVICES="80   22   25   110   8000   23   20   21   3306   "
for   x   in   $SERVICES
Do
iptables   -A   INPUT   -p   tcp   --dport   $x   -m   state   --state   NEW   -j   ACCEPT  
Done
For variable in values
/bin/sh!
For I in a B C string list a B C
Strings are separated by spaces, no parentheses, no commas, and are assigned to variables I in turn
Variable does not$
Do
echo "i is $i"
Done
[macg@machome ~]$ sh test.sh
I is a
I is b
I is C
In for in, variable and * are not equivalent
/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 represents the entire path, not the part before. H in *. H
correction
/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
Example 2:
for i in /etc/profile.d/*.sh
Do
$i
Done
$I stands for / etc / profile.d/color.sh,
/etc/profile.d/alias.sh, /etc/profile.d/default.sh
For in traverses (command line, function) parameters
Test ()
{
Local I
for i in $* ; do
echo "i is $i"
Done
}
$* is a string: save all parameters as "Parameter1 parameter2..."
$I is the applied representation of variable I
[macg@machome ~]$ sh test.sh p1 p2 p3 p4
I is P1
I is P2
I is P3
I is P4
For in statement is used with wildcard * to batch process files
Batch change file name
[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 is equivalent to an array of strings, which are assigned to I in turn
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
The for in statement is used with ` ` and $() to combine multiple lines into one line, which is actually a string array
for i in $(ls *.txt)
Do
Echo $i
Done
[macg@machome ~]$ sh test
111-tmp.txt
111.txt
22.txt
33.txt
In other words, use for in to overcome the defect of combining multiple lines of ` ` and $() into one line
Using for in to automatically traverse strings by spaces, traverse multiple directories
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