for循環、while循環、break循環、continue結束本次循環、exit退出整個腳本
阿新 • • 發佈：2018-02-07
核心 一次 src 郵件告警 aso 分隔符 fuse crypt 語句 for循環
- for循環案例1
#打印1到100 [root@garytao-01 shell]# vi for1.sh [root@garytao-01 shell]# cat for1.sh #!/bin/bash for i in `seq 1 100 ` do echo $i done [root@garytao-01 shell]# sh for1.sh 1 2 3 4 5 6 7 8 9 10 11 ... #打印數字疊加的值 [root@garytao-01 shell]# vi for1.sh [root@garytao-01 shell]# cat for1.sh #!/bin/bash sum=0 for i in `seq 1 100 ` do sum=$[$sum+$i] #核心語句 done echo $sum [root@garytao-01 shell]# sh for1.sh 5050 #每次循環相加的值 [root@garytao-01 shell]# vi for1.sh [root@garytao-01 shell]# cat for1.sh #!/bin/bash sum=0 for i in `seq 1 100` do echo "$sum + $i" sum=$[$sum+$i] echo $sum done echo $sum [root@garytao-01 shell]# sh for1.sh 0 + 1 1 1 + 2 3 3 + 3 6 .... 4950 + 100 5050
- for循環案例2
[root@garytao-01 shell]# vi for2.sh [root@garytao-01 shell]# cat for2.sh #!/bin/bash cd /etc/ for a in ls /etc/ do if [ -d $a ] then echo $a ls $a fi done [root@garytao-01 shell]# sh for2.sh /etc/ adjtime exports.d ld.so.conf.d pki shadow- aliases favicon.png lftp.conf plymouth shells aliases.db filesystems libaudit.conf pm skel alternatives firewalld libnl polkit-1 ssh anacrontab fonts libuser.conf popt.d ssl asound.conf fstab locale.conf postfix statetab audisp fuse.conf localtime ppp statetab.d audit gcrypt login.defs prelink.conf.d subgid bash_completion.d GeoIP.conf logrotate.conf printcap subuid
- for循環會把命令空格及回車當作是一個分隔符，這個在寫腳本的時候需要註意，如下示例
while循環
- 語法 while 條件; do … ; done
需求：每隔半分鐘檢查系統負載，當系統負載大於10的時候就發一封郵件告警。
腳本示例：
[root@garytao-01 aming]# vi while1.sh [root@garytao-01 aming]# cat while1.sh #!/bin/bash while true do load=`w|head -1|awk -F ‘load average: ‘ ‘{print $2}‘|cut -d. -f1` if [ $load -gt 10 ] then /usr/local/sbin/mail.py [email protected] "load high" "$load" fi sleep 30 done [root@garytao-01 aming]# sh -x while1.sh + true ++ w ++ head -1 ++ awk -F ‘load average: ‘ ‘{print $2}‘ ++ cut -d. -f1 + load=0 + ‘[‘ 0 -gt 10 ‘]‘ + sleep 30 + true ++ w ++ head -1 ++ awk -F ‘load average: ‘ ‘{print $2}‘ ++ cut -d. -f1 + load=0 + ‘[‘ 0 -gt 10 ‘]‘ + sleep 30 ^C [root@garytao-01 aming]#
需求：在循環過程中需要人為的輸入一個數字
腳本示例：
[root@garytao-01 shell]# vim while2.sh
[root@garytao-01 shell]# cat while2.sh
#!/bin/bash
while :
do
read -p "Please input a number: " n
if [ -z "$n" ]
then
echo "you need input sth."
continue
fi
n1=`echo $n|sed ‘s/[0-9]//g‘`
if [ ! -z "$n1" ]
then
echo "you just only input numbers."
continue
fi
break
done
echo $n
[root@garytao-01 shell]# sh -x while2.sh
+ :
+ read -p ‘Please input a number: ‘ n
Please input a number:
+ ‘[‘ -z ‘‘ ‘]‘
+ echo ‘you need input sth.‘
you need input sth.
+ continue
+ :
+ read -p ‘Please input a number: ‘ n
Please input a number: 23
+ ‘[‘ -z 23 ‘]‘
++ echo 23
++ sed ‘s/[0-9]//g‘
+ n1=
+ ‘[‘ ‘!‘ -z ‘‘ ‘]‘
+ break
+ echo 23
23
[root@garytao-01 shell]# vim while2.sh
[root@garytao-01 shell]# cat while2.sh
#!/bin/bash
while :
do
read -p "Please input a number: " n
if [ -z "$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@garytao-01 shell]# sh -x while2.sh
+ :
+ read -p ‘Please input a number: ‘ n
Please input a number:
+ ‘[‘ -z ‘‘ ‘]‘
+ echo ‘you need input sth.‘
you need input sth.
+ continue
+ :
+ read -p ‘Please input a number: ‘ n
Please input a number: 32kgg
+ ‘[‘ -z 32kgg ‘]‘
++ echo 32kgg
++ sed ‘s/[0-9]//g‘
+ n1=kgg
+ ‘[‘ -n kgg ‘]‘
+ echo ‘you just only input numbers.‘
you just only input numbers.
+ continue
+ :
+ read -p ‘Please input a number: ‘ n
Please input a number: 45
+ ‘[‘ -z 45 ‘]‘
++ echo 45
++ sed ‘s/[0-9]//g‘
+ n1=
+ ‘[‘ -n ‘‘ ‘]‘
+ break
+ echo 45
45break跳出循環
- 把整個循環退出
[root@garytao-01 aming]# vi break1.sh
[root@garytao-01 aming]# 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 aaaaa
[root@garytao-01 aming]# sh break1.sh
1
1
2
2
3
aaaaa
[root@garytao-01 aming]# 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 aaaaa
aaaaa
[root@garytao-01 aming]#
continue結束本次循環
- 忽略continue之下的代碼，直接進行下一次循環
[root@garytao-01 aming]# vi continue.sh
[root@garytao-01 aming]# cat continue.sh
#!/bin/bash
for i in `seq 1 5`
do
echo $i
if [ $i -eq 3 ]
then
continue
fi
echo $i
done
echo aaaaa
[root@garytao-01 aming]# sh continue.sh
1
1
2
2
3
4
4
5
5
aaaaa
[root@garytao-01 aming]# sh -x continue.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 aaaaa
aaaaa
[root@garytao-01 aming]#
exit退出整個腳本
- 直接退出整個腳本，腳本示例
[root@garytao-01 aming]# vi exit.sh
[root@garytao-01 aming]# cat exit.sh
#!/bin/bash
for i in `seq 1 5`
do
echo $i
if [ $i -eq 3 ]
then
exit
fi
echo $i
done
echo aaaaa
[root@garytao-01 aming]# sh exit.sh
1
1
2
2
3
[root@garytao-01 aming]# sh -x exit.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
[root@garytao-01 aming]#
for循環、while循環、break循環、continue結束本次循環、exit退出整個腳本