23-Linux-shell脚本进阶篇（三）

mac2024-08-06 53

shell脚本进阶篇（三）

函数

函数由两部分组成：函数名和函数体

格式：

语法一： f_name (){ ...函数体... } 语法二： function f_name { ...函数体... } 语法三： function f_name(){ ...函数体... }

函数function是由若干条shell命令组成的语句块，实现代码重用和模块化编程

函数function并不是一个单独的进程，不能独立运行；它是shell程序的一部分

函数与shell程序的区别：

shell程序在子shell中运行函数在当前shell中运行

删除shell函数：unset function_name

示例：

切换至 etc 目录

[root@CentOS7 data]# fk(){ > cd /etc > } [root@CentOS7 data]# fk [root@CentOS7 etc]#

删除该函数

或者用户退出系统后，自动删除

[root@CentOS7 etc]# unset fk [root@CentOS7 etc]# fk bash: fk: command not found... Similar command is: 'fc' [root@CentOS7 etc]#

在脚本中定义及使用函数

函数在使用前必须定义，因此应将函数定义放在脚本开始部分，直至shell首次发现它后才能使用调用函数仅使用其函数名即可

使用函数检查磁盘最大使用率

[root@CentOS7 etc]# vim max_disk.sh #!/bin/bash # Maximum disk occupancy maxdf() { echo `df -h |grep "^/dev/sd"|tr -s " " |cut -d" " -f5 |sort -n |cut -d"%" -f1 |tail -1` } echo Maxdf=`maxdf` #运行脚本 [root@CentOS7 etc]# sh max_disk.sh Maxdf=17 使子进程也可使用：声明：export -f function_name查看：export -f 或 declare -xf [root@CentOS7 ~]# go(){ #创建一个函数 > cd /data/scripts/ > ls > \rm * > touch firstfun > echo {1..9} > firstfun > } [root@CentOS7 ~]# export -f go #声明该函数在其子进程依旧有效 [root@CentOS7 ~]# export -f #查看函数 go () { cd /data/scripts/; ls --color=auto; \rm *; touch firstfun; echo {1..9} > firstfun } declare -fx go [root@CentOS7 ~]# go #执行一次该函数 f1.apk f2.apk f3.apk f4.apk f5.apk f6.apk f7.apk f8.apk f9.apk [root@CentOS7 scripts]# ls firstfun [root@CentOS7 scripts]# cat firstfun 1 2 3 4 5 6 7 8 9 [root@CentOS7 scripts]# unset go #删除该函数 [root@CentOS7 scripts]# export -f #重新查看该函数 [root@CentOS7 scripts]# go #重新执行该函数 bash: go: command not found... [root@CentOS7 scripts]# export -f go #重新声明该函数 -bash: export: go: not a function 或者 [root@CentOS7 scripts]# hello(){ > echo "hello,are you ok?" > } [root@CentOS7 scripts]# vim hello_fun.sh #!/bin/bash haha(){ hello } echo `haha` [root@CentOS7 scripts]# export -f hello #运行脚本 [root@CentOS7 scripts]# sh hello_fun.sh hello,are you ok? 又或者 [root@CentOS7 scripts]# vim one.sh #!/bin/bash one () { echo "let's go to play computer?" } [root@CentOS7 scripts]# vim two.sh #!/bin/bash two () { one three } echo "`two`" #添加" "可保留原有格式，而非打印在同一行 [root@CentOS7 scripts]# vim three.sh #!/bin/bash three () { echo "That's good idea." } 若未执行 export -f function_name 则会出现： #运行脚本 [root@CentOS7 scripts]# sh two.sh two.sh: line 3: one: command not found two.sh: line 4: three: command not found [root@CentOS7 scripts]#

[root@CentOS7 scripts]# . one.sh [root@CentOS7 scripts]# . three.sh [root@CentOS7 scripts]# export -f one [root@CentOS7 scripts]# export -f three #运行脚本 [root@CentOS7 scripts]# sh two.sh let's go to play computer? That's good idea.

批量创建用户

#准备用户名单 [root@CentOS7 data]# vim name.txt lisuo sunxiaobo lipengbin mahuateng xietingfeng zhaoritian mayun laowang [root@CentOS7 data]# vim batch_user2.sh #!/bin/bash . /etc/init.d/functions if [ "$1" = '-c' ];then for USER in `cat /data/name.txt`;do if id $USER &> /dev/null;then action "$USER is exist." false else useradd $USER echo $USER | passwd --stdin $USER &> /dev/null action "$USER is created." true fi done elif [ "$1" = '-r' ];then for USER in `cat /data/name.txt`;do userdel -r $USER &> /dev/null echo "$USER is removed." done else echo "Usage: `basename $0` -c |-r " fi #运行脚本 [root@CentOS7 data]# sh batch_user2.sh -r lisuo is removed. sunxiaobo is removed. lipengbin is removed. mahuateng is removed. xietingfeng is removed. zhaoritian is removed. mayun is removed. laowang is removed. #运行脚本 [root@CentOS7 data]# sh batch_user2.sh -c lisuo is created. [ OK ] sunxiaobo is created. [ OK ] lipengbin is created. [ OK ] mahuateng is created. [ OK ] xietingfeng is created. [ OK ] zhaoritian is created. [ OK ] mayun is created. [ OK ] laowang is created. [ OK ] [root@CentOS7 data]# #查看执行脚本后是否成功创建用户 [root@CentOS7 data]# cat /etc/passwd .................................... lisuo:x:1002:1002::/home/lisuo:/bin/bash sunxiaobo:x:1003:1003::/home/sunxiaobo:/bin/bash lipengbin:x:1004:1004::/home/lipengbin:/bin/bash mahuateng:x:1005:1005::/home/mahuateng:/bin/bash xietingfeng:x:1006:1006::/home/xietingfeng:/bin/bash zhaoritian:x:1007:1007::/home/zhaoritian:/bin/bash mayun:x:1008:1008::/home/mayun:/bin/bash laowang:x:1009:1009::/home/laowang:/bin/bash

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