for循環，while循環
阿新 • • 發佈：2018-04-20
for while循環for循環
1.語法：for in do done
[root@weixing01 shell]# cat for.sh
#!/bin/bash
sum=0
for i in `seq 1 100`
do
sum=$[$sum+$i]
done
echo $sum
[root@weixing01 shell]# sh -x for.sh + sum=0 ++ seq 1 100 + for i in ‘`seq 1 100`‘ + sum=1 + for i in ‘`seq 1 100`‘ + sum=3 + for i in ‘`seq 1 100`‘ + sum=6 + for i in ‘`seq 1 100`‘ + sum=10 + for i in ‘`seq 1 100`‘ + sum=15 + for i in ‘`seq 1 100`‘ + sum=21 + for i in ‘`seq 1 100`‘ + sum=28 + for i in ‘`seq 1 100`‘ + sum=36 + for i in ‘`seq 1 100`‘ + sum=45 + for i in ‘`seq 1 100`‘ + sum=55 + for i in ‘`seq 1 100`‘ + sum=66 + for i in ‘`seq 1 100`‘ + sum=78 + for i in ‘`seq 1 100`‘ + sum=91 + for i in ‘`seq 1 100`‘ + sum=105 + for i in ‘`seq 1 100`‘ + sum=120 + for i in ‘`seq 1 100`‘ + sum=136 + for i in ‘`seq 1 100`‘ + sum=153 + for i in ‘`seq 1 100`‘ + sum=171 + for i in ‘`seq 1 100`‘ + sum=190 + for i in ‘`seq 1 100`‘ + sum=210 + for i in ‘`seq 1 100`‘ + sum=231 + for i in ‘`seq 1 100`‘ + sum=253 + for i in ‘`seq 1 100`‘ + sum=276 + for i in ‘`seq 1 100`‘ + sum=300 + for i in ‘`seq 1 100`‘ + sum=325 + for i in ‘`seq 1 100`‘ + sum=351 + for i in ‘`seq 1 100`‘ + sum=378 + for i in ‘`seq 1 100`‘ + sum=406 + for i in ‘`seq 1 100`‘ + sum=435 + for i in ‘`seq 1 100`‘ + sum=465 + for i in ‘`seq 1 100`‘ + sum=496 + for i in ‘`seq 1 100`‘ + sum=528 + for i in ‘`seq 1 100`‘ + sum=561 + for i in ‘`seq 1 100`‘ + sum=595 + for i in ‘`seq 1 100`‘ + sum=630 + for i in ‘`seq 1 100`‘ + sum=666 + for i in ‘`seq 1 100`‘ + sum=703 + for i in ‘`seq 1 100`‘ + sum=741 + for i in ‘`seq 1 100`‘ + sum=780 + for i in ‘`seq 1 100`‘ + sum=820 + for i in ‘`seq 1 100`‘ + sum=861 + for i in ‘`seq 1 100`‘ + sum=903 + for i in ‘`seq 1 100`‘ + sum=946 + for i in ‘`seq 1 100`‘ + sum=990 + for i in ‘`seq 1 100`‘ + sum=1035 + for i in ‘`seq 1 100`‘ + sum=1081 + for i in ‘`seq 1 100`‘ + sum=1128 + for i in ‘`seq 1 100`‘ + sum=1176 + for i in ‘`seq 1 100`‘ + sum=1225 + for i in ‘`seq 1 100`‘ + sum=1275 + for i in ‘`seq 1 100`‘ + sum=1326 + for i in ‘`seq 1 100`‘ + sum=1378 + for i in ‘`seq 1 100`‘ + sum=1431 + for i in ‘`seq 1 100`‘ + sum=1485 + for i in ‘`seq 1 100`‘ + sum=1540 + for i in ‘`seq 1 100`‘ + sum=1596 + for i in ‘`seq 1 100`‘ + sum=1653 + for i in ‘`seq 1 100`‘ + sum=1711 + for i in ‘`seq 1 100`‘ + sum=1770 + for i in ‘`seq 1 100`‘ + sum=1830 + for i in ‘`seq 1 100`‘ + sum=1891 + for i in ‘`seq 1 100`‘ + sum=1953 + for i in ‘`seq 1 100`‘ + sum=2016 + for i in ‘`seq 1 100`‘ + sum=2080 + for i in ‘`seq 1 100`‘ + sum=2145 + for i in ‘`seq 1 100`‘ + sum=2211 + for i in ‘`seq 1 100`‘ + sum=2278 + for i in ‘`seq 1 100`‘ + sum=2346 + for i in ‘`seq 1 100`‘ + sum=2415 + for i in ‘`seq 1 100`‘ + sum=2485 + for i in ‘`seq 1 100`‘ + sum=2556 + for i in ‘`seq 1 100`‘ + sum=2628 + for i in ‘`seq 1 100`‘ + sum=2701 + for i in ‘`seq 1 100`‘ + sum=2775 + for i in ‘`seq 1 100`‘ + sum=2850 + for i in ‘`seq 1 100`‘ + sum=2926 + for i in ‘`seq 1 100`‘ + sum=3003 + for i in ‘`seq 1 100`‘ + sum=3081 + for i in ‘`seq 1 100`‘ + sum=3160 + for i in ‘`seq 1 100`‘ + sum=3240 + for i in ‘`seq 1 100`‘ + sum=3321 + for i in ‘`seq 1 100`‘ + sum=3403 + for i in ‘`seq 1 100`‘ + sum=3486 + for i in ‘`seq 1 100`‘ + sum=3570 + for i in ‘`seq 1 100`‘ + sum=3655 + for i in ‘`seq 1 100`‘ + sum=3741 + for i in ‘`seq 1 100`‘ + sum=3828 + for i in ‘`seq 1 100`‘ + sum=3916 + for i in ‘`seq 1 100`‘ + sum=4005 + for i in ‘`seq 1 100`‘ + sum=4095 + for i in ‘`seq 1 100`‘ + sum=4186 + for i in ‘`seq 1 100`‘ + sum=4278 + for i in ‘`seq 1 100`‘ + sum=4371 + for i in ‘`seq 1 100`‘ + sum=4465 + for i in ‘`seq 1 100`‘ + sum=4560 + for i in ‘`seq 1 100`‘ + sum=4656 + for i in ‘`seq 1 100`‘ + sum=4753 + for i in ‘`seq 1 100`‘ + sum=4851 + for i in ‘`seq 1 100`‘ + sum=4950 + for i in ‘`seq 1 100`‘ + sum=5050 + echo 5050 5050
2.案例2：
[root@weixing01 shell]# cat for2.sh
#!/bin/bash
cd /etc/
for a in ls /etc/
do
if [ -d $a ]
then
ls $a
fi
done
[root@weixing01 shell]# sh for2.sh adjtime group named.iscdlv.key rsyslog.d aliases group- named.rfc1912.zones rwtab aliases.db grub2.cfg named.root.key rwtab.d alternatives grub.d netconfig samba anacrontab gshadow NetworkManager sasl2 asound.conf gshadow- networks screenrc audisp gss nfs.conf securetty audit gssproxy nfsmount.conf security bash_completion.d host.conf nsswitch.conf selinux bashrc hostname nsswitch.conf.bak services binfmt.d hosts odbcinst.ini sestatus.conf centos-release hosts.allow openldap shadow centos-release-upstream hosts.deny opt shadow-
3.註意for循環中以空格為分隔符：
[root@weixing01 weix]# touch 1 2 [root@weixing01 weix]# touch 3\ 4.txt [root@weixing01 weix]# ls 1 2 3 4.txt [root@weixing01 weix]# ls3 -bash: ls3: 未找到命令 [root@weixing01 weix]# ls 3 ls: 無法訪問3: 沒有那個文件或目錄 [root@weixing01 weix]# ls -l 總用量 0 -rw-r--r-- 1 root root 0 4月 19 22:16 1 -rw-r--r-- 1 root root 0 4月 19 22:16 2 -rw-r--r-- 1 root root 0 4月 19 22:16 3 4.txt [root@weixing01 weix]# for i in `ls ./`; do echo $i ; done 1 2 3 4.txt
while循環
1.案例1：
[root@weixing01 shell]# cat whil2.sh
#!/bin/bash
while true
do
load=`w|head 1|awk -F ‘load average: ‘ ‘{print $2}‘ |cut -d. -f1`
if [ $load -gt 10 ]
then
echo "bbb"
fi
sleep 30
done
[root@weixing01 shell]# sh -x whil2.sh
+ true
++ w
++ head 1
head: 無法打開"1" 讀取數據: 沒有那個文件或目錄
++ awk -F ‘load average: ‘ ‘{print $2}‘
++ cut -d. -f1
+ load=
+ ‘[‘ -gt 10 ‘]‘
whil2.sh: 第 5 行:[: -gt: 期待一元表達式
+ sleep 30
2.案例2
[root@weixing01 shell]# cat while3.sh
#!/bin/bash
while :
do
read -p "Please input a number: " n
if [ -z "$n" ]
then
echo "you need input sth."
continue
fi
n1=`echo $n|sed ‘s/[0-9]//g‘`
if [ -n "$n1" ]
then
echo "you just only input numbers."
continue
fi
break
done
echo $n
[root@weixing01 shell]# sh -x while3.sh
+ :
+ read -p ‘Please input a number: ‘ n
Please input a number: 123fjkagj
+ ‘[‘ -z 123fjkagj ‘]‘
++ echo 123fjkagj
++ sed ‘s/[0-9]//g‘
+ n1=fjkagj
+ ‘[‘ -n fjkagj ‘]‘
+ echo ‘you just only input numbers.‘
you just only input numbers.
+ continue
+ :
+ read -p ‘Please input a number: ‘ n
Please input a number: 123124
+ ‘[‘ -z 123124 ‘]‘
++ echo 123124
++ sed ‘s/[0-9]//g‘
+ n1=
+ ‘[‘ -n ‘‘ ‘]‘
+ break
+ echo 123124
123124
break跳出循環
[root@weixing01 shell]# cat break1.sh
#!/bin/bash
for i in `seq 1 5`
do
echo $i
if [ $i -eq 3 ]
then
break
fi
echo $i
done
echo aaaa
[root@weixing01 shell]# sh -x break1.sh
++ seq 1 5
+ for i in ‘`seq 1 5`‘
+ echo 1
1
+ ‘[‘ 1 -eq 3 ‘]‘
+ echo 1
1
+ for i in ‘`seq 1 5`‘
+ echo 2
2
+ ‘[‘ 2 -eq 3 ‘]‘
+ echo 2
2
+ for i in ‘`seq 1 5`‘
+ echo 3
3
+ ‘[‘ 3 -eq 3 ‘]‘
+ break
+ echo aaaa
aaaa
continue結束本次循環
[root@weixing01 shell]# cat continue1.sh
#!/bin/bash
for i in `seq 1 5`
do
echo $i
if [ $i -eq 3 ]
then
continue
fi
echo $i
done
echo aaaa
[root@weixing01 shell]# sh -x continue1.sh
++ seq 1 5
+ for i in ‘`seq 1 5`‘
+ echo 1
1
+ ‘[‘ 1 -eq 3 ‘]‘
+ echo 1
1
+ for i in ‘`seq 1 5`‘
+ echo 2
2
+ ‘[‘ 2 -eq 3 ‘]‘
+ echo 2
2
+ for i in ‘`seq 1 5`‘
+ echo 3
3
+ ‘[‘ 3 -eq 3 ‘]‘
+ continue
+ for i in ‘`seq 1 5`‘
+ echo 4
4
+ ‘[‘ 4 -eq 3 ‘]‘
+ echo 4
4
+ for i in ‘`seq 1 5`‘
+ echo 5
5
+ ‘[‘ 5 -eq 3 ‘]‘
+ echo 5
5
+ echo aaaa
aaaa
exit直接退出腳本
[root@weixing01 shell]# cat exit1.sh
#!/bin/bash
for i in `seq 1 5`
do
echo $i
if [ $i -eq 3 ]
then
exit
fi
echo $i
done
echo aaaa
[root@weixing01 shell]# sh -x exit1.sh
++ seq 1 5
+ for i in ‘`seq 1 5`‘
+ echo 1
1
+ ‘[‘ 1 -eq 3 ‘]‘
+ echo 1
1
+ for i in ‘`seq 1 5`‘
+ echo 2
2
+ ‘[‘ 2 -eq 3 ‘]‘
+ echo 2
2
+ for i in ‘`seq 1 5`‘
+ echo 3
3
+ ‘[‘ 3 -eq 3 ‘]‘
+ exit
for循環，while循環