for循環，while循環，break跳出循環，continue結束本次循環，exit直接退出腳本
阿新 • • 發佈：2018-07-14
href 變量名 average 變量 inpu code 支持 bash eas for循環
- 語法：for 變量名 in 條件; do …; done
- 案列1，算出1到10的數字相加等於多少並打印出過程
[root@akuilinux01 shell]# cat for1.sh #!/bin/bash sum=0 for i in `seq 1 10` do sum=$[$sum+$i] echo "$sum + $i" done echo $sum [root@akuilinux01 shell]# sh -x for1.sh + sum=0 ++ seq 1 10 + for i in ‘`seq 1 10`‘ + sum=1 + echo ‘1 + 1‘ 1 + 1 + for i in ‘`seq 1 10`‘ + sum=3 + echo ‘3 + 2‘ 3 + 2 + for i in ‘`seq 1 10`‘ + sum=6 + echo ‘6 + 3‘ 6 + 3 + for i in ‘`seq 1 10`‘ + sum=10 + echo ‘10 + 4‘ 10 + 4 + for i in ‘`seq 1 10`‘ + sum=15 + echo ‘15 + 5‘ 15 + 5 + for i in ‘`seq 1 10`‘ + sum=21 + echo ‘21 + 6‘ 21 + 6 + for i in ‘`seq 1 10`‘ + sum=28 + echo ‘28 + 7‘ 28 + 7 + for i in ‘`seq 1 10`‘ + sum=36 + echo ‘36 + 8‘ 36 + 8 + for i in ‘`seq 1 10`‘ + sum=45 + echo ‘45 + 9‘ 45 + 9 + for i in ‘`seq 1 10`‘ + sum=55 + echo ‘55 + 10‘ 55 + 10 + echo 55 55 - 文件列表循環，列出/root/shell/目錄下子目錄中的所有文件
[root@akuilinux01 shell]# cat for2.sh #!/bin/bash cd /root/shell/ for a in `ls /root/shell` do if [ -d $a ] then ls $a fi done [root@akuilinux01 shell]# sh -x for2.sh + cd /root/shell/ ++ ls /root/shell + for a in ‘`ls /root/shell`‘ + ‘[‘ -d 1 ‘]‘ + ls 1 1.txt 2.txt 3.txt + for a in ‘`ls /root/shell`‘ + ‘[‘ -d 1.sh ‘]‘ + for a in ‘`ls /root/shell`‘ + ‘[‘ -d 2 ‘]‘ + ls 2 a.txt b.txt c.txt + for a in ‘`ls /root/shell`‘ + ‘[‘ -d 3 ‘]‘ + ls 3 + for a in ‘`ls /root/shell`‘ + ‘[‘ -d 4 ‘]‘ + ls 4 + for a in ‘`ls /root/shell`‘ + ‘[‘ -d case.sh ‘]‘ + for a in ‘`ls /root/shell`‘ + ‘[‘ -d file1.sh ‘]‘ + for a in ‘`ls /root/shell`‘ + ‘[‘ -d file2.sh ‘]‘ + for a in ‘`ls /root/shell`‘ + ‘[‘ -d for1.sh ‘]‘ + for a in ‘`ls /root/shell`‘ + ‘[‘ -d for2.sh ‘]‘ + for a in ‘`ls /root/shell`‘ + ‘[‘ -d if1.sh ‘]‘ + for a in ‘`ls /root/shell`‘ + ‘[‘ -d if2.sh ‘]‘ + for a in ‘`ls /root/shell`‘ + ‘[‘ -d if3.sh ‘]‘ + for a in ‘`ls /root/shell`‘ + ‘[‘ -d if4.sh ‘]‘ [root@akuilinux01 shell]# sh for2.sh 1.txt 2.txt 3.txt a.txt b.txt c.txt - for循環是以空格和回車作為分割符，所以不支持列出帶有空格的文件名的文件
while循環
- 語法 while 條件; do … ; done
- 案列：當系統的負載大於10的時候就發一封郵件
[root@akuilinux01 shell]# cat while1.sh #!/bin/bash #死循環,:是一個死循環，也可以寫成1或者true while : do #截取負載的值並賦給變量load load=`w|head -1|awk -F ‘load average: ‘ ‘{print $2}‘|cut -d. -f1` #如果負載大於10就報警並發送郵件，設置30秒查一次 if [ $load -gt 10 ] then /usr/lib/zabbix/alertscripts/mail.py [email protected] "load is high:$load" fi sleep 30 done [root@akuilinux01 shell]# sh -x while1.sh + : ++ head -1 ++ cut -d. -f1 ++ w ++ awk -F ‘load average: ‘ ‘{print $2}‘ + load=0 + ‘[‘ 0 -gt 10 ‘]‘ + sleep 30 ^C - 截取負載的值
[root@akuilinux01 shell]# uptime|awk -F ‘load average: ‘ ‘{print $2}‘ 0.01, 0.03, 0.05 [root@akuilinux01 shell]# uptime|awk -F ‘load average: ‘ ‘{print $2}‘|cut -d. -f1 0 #w|head -1也可以寫成uptime [root@akuilinux01 shell]# w |head -1 01:02:36 up 58 min, 1 user, load average: 0.07, 0.04, 0.05 [root@akuilinux01 shell]# uptime 01:02:46 up 59 min, 1 user, load average: 0.06, 0.04, 0.05 - 案列2：數字輸入交互
[root@akuilinux01 shell]# cat while2.sh #!/bin/bash while : do read -p "Please input a number: " n #如果你什麽也沒輸入 if [ -z "$n" ] then echo "你需要輸入一個數字" #從頭開始循環 continue fi #過濾數字並賦予n1 n1=`echo $n|sed ‘s/[0-9]//g‘` #如果n1不為空，提示 if [ -n "$n1" ] then echo "你只能輸入一個純數字" continue fi #退出循環 break done echo $n [root@akuilinux01 shell]# sh while2.sh Please input a number: 你需要輸入一個數字 Please input a number: a 你只能輸入一個純數字 Please input a number: 2 2break跳出循環
- 案列：當i等於3時，跳出循環並打印aaaa
[root@akuilinux01 shell]# cat break.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@akuilinux01 shell]# sh -x break.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 aaaacontinue結束本次循環
- 忽略continue之下的代碼，直接進行下一次循環
- 案列：當i不等於3的時候打印出i，當i等於3的時候退出本次循環不打印
[root@akuilinux01 shell]# cat continue.sh #!/bin/bash for i in `seq 1 5` do if [ $i -eq 3 ] then continue fi echo $i done echo aaaa [root@akuilinux01 shell]# sh -x continue.sh ++ seq 1 5 + for i in ‘`seq 1 5`‘ + ‘[‘ 1 -eq 3 ‘]‘ + echo 1 1 + for i in ‘`seq 1 5`‘ + ‘[‘ 2 -eq 3 ‘]‘ + echo 2 2 + for i in ‘`seq 1 5`‘ + ‘[‘ 3 -eq 3 ‘]‘ + continue + for i in ‘`seq 1 5`‘ + ‘[‘ 4 -eq 3 ‘]‘ + echo 4 4 + for i in ‘`seq 1 5`‘ + ‘[‘ 5 -eq 3 ‘]‘ + echo 5 5 + echo aaaa aaaaexit直接退出腳本
- 案列：當i不等於3的時候打印出i，當i等於3的時候直接退出腳本
[root@akuilinux01 shell]# cat exit.sh #!/bin/bash for i in `seq 1 5` do if [ $i -eq 3 ] then exit fi echo $i done echo aaaa [root@akuilinux01 shell]# sh -x exit.sh ++ seq 1 5 + for i in ‘`seq 1 5`‘ + ‘[‘ 1 -eq 3 ‘]‘ + echo 1 1 + for i in ‘`seq 1 5`‘ + ‘[‘ 2 -eq 3 ‘]‘ + echo 2 2 + for i in ‘`seq 1 5`‘ + ‘[‘ 3 -eq 3 ‘]‘ + exit [root@akuilinux01 shell]# sh exit.sh 1 2擴展
- select用法
for循環，while循環，break跳出循環，continue結束本次循環，exit直接退出腳本