第10讲 Shell编程.doc

第10讲 Shell编程Shell编程语法：2Shell 结构：2创建shell程序的步骤：2Shell变量：2Shell命令：4read 命令：从键盘读入数据，赋给变量4expr命令：4变量测试语句：4字符串测试5整数测试5文件测试6流控制语句：6exit语句：6If语句：6多个条件的联合：7for done 语句：7Select语句：8Case esac语句：8While语句：9Until语句：10跳出循环：break和continue11Shift 指令：11函数应用：12shell脚本调试：13Awk命令应用：13案例：自动生成系统信息13案例：自动把用户踢出系统14案例：批量添加用户14案例：删除用户15案例：显示用户信息16案例：17Shell编程语法：Shell 结构：1.#!指定执行脚本的shell2.#注释行3.命令和控制结构案例：#!/bin/sh /指定执行脚本的shell#This is to show what a example looks like. /注释行echo Our first example /此行是命令echo # This inserts an empty line in output.echo We are currently in the following directory./bin/pwdechoecho This directory contains the following files/bin/ls创建shell程序的步骤：第一步：创建一个包含命令和控制结构的文件 ：vi example第二步：修改这个文件的权限是它可以执行使用chmod u+x第三步：执行 .example(也可以使用“sh example”执行)Shell变量：Shell有两类变量：临时变量：shell程序内部定义的，其使用范围仅限于定义它的程序，对其它程序不可见。包括：用户自定义变量，位置变量。 永久变量：是环境变量，其值不随shell脚本的执行结束而消失。用户自定义变量：变量名=赋值定义是赋值： 如：num=1使用变量时，要在变量名前加上前缀“$”使用echo命令查看变量值：案例：rootlocalhost shell.example# num=1rootlocalhost shell.example# echo $num1rootlocalhost shell.example#变量之间赋值：rootlocalhost shell.example# num2=$numrootlocalhost shell.example# echo $num21rootlocalhost shell.example#命令的结果赋给变量：案例：time=date /用命令替换符rootlocalhost shell.example# time=daterootlocalhost shell.example# echo $timeMon May 23 11:27:28 CST 2011列出所有的变量：set命令案例：rootlocalhost shell.example# setBASH=/bin/bashBASH_ARGC=()BASH_ARGV=()BASH_LINENO=()BASH_SOURCE=()BASH_VERSINFO=(0=3 1=2 2=25 3=1 4=release 5=i686-redhat-linux-gnu).删除变量：unset命令 格式：unset 变量名包含多个字的变量的方法：变量赋值单引号和双引号区别：双引号变量读取取值单引号变量会不读值显示案例：rootlocalhost shell.example# NAME=zhuangqianlinrootlocalhost shell.example# my=$NAME is a studentrootlocalhost shell.example# my1=$NAME is a studentrootlocalhost shell.example# echo $my$NAME is a student /单引号变量会不读值显示rootlocalhost shell.example# echo $my1zhuangqianlin is a student /双引号变量读取取值rootlocalhost shell.example#位置变量和特殊变量：1.由命令行上的位置确定的参数称位置参数（位置变量） 2.特殊变量$? 用来判断一个命令执行的正误Shell命令：read 命令：从键盘读入数据，赋给变量例如： rootlocalhost shell.example# read name1 name2 name3shaolin1 shaolin2 shaolin3 /此处是在命令提示符下从键盘上输入的值rootlocalhost shell.example# echo $name1 $name2 $name3shaolin1 shaolin2 shaolin3rootlocalhost shell.example#expr命令：案例1：简单运算rootlocalhost shell.example# expr 3 + 58rootlocalhost shell.example# expr 3 - 5-2rootlocalhost shell.example# expr 3 / 50rootlocalhost shell.example# expr 3 * 515案例2：复杂运算rootlocalhost shell.example# vi test.sha=20b=60c=expr $a + $b /用替换符:echo $crootlocalhost shell.example# sh test.sh80注意：运算符左右两侧必须有空格 乘法运算（*）是必须用转义字符. 形式为：*变量测试语句：作用：用来测试变量是否相等、是否为空、文件类型等。格式：test 测试条件 测试范围：整数、字符串、文件字符串测试 整数测试文件测试变量测试语句一般不单独使用，一般作为if语句的测试条件如： if test d $1 then. fi变量测试语句可用进行简化，如：Test d $1 等价于 -d $1流控制语句：作用：用于控制shell程序的流程exit语句：退出程序执行返回0：表示正常退出返回1：表示非正常退出 例如：exit 0If语句：格式：第一种：iffthen.fi第二种：ifthen.else .fi第三种：多个条件的联合：for done 语句：格式：案例：rootlocalhost shell.example# vi for#!/bin/shfor DAY in Sunday Monday Tuesday Wednesday Thursday Friday Saturdaydo echo The day is : $DAYdonerootlocalhost shell.example# sh forThe day is : SundayThe day is : MondayThe day is : TuesdayThe day is : WednesdayThe day is : ThursdayThe day is : FridayThe day is : SaturdaySelect语句：格式：范例：rootlocalhost shell.example# vi select#!/bin/sh# select Usageecho What is your favourite OS?select var in Linux UNIX Windows Otherdo breakdoneecho You have selected $varrootlocalhost shell.example# sh selectWhat is your favourite OS?1) Linux2) UNIX3) Windows4) Other#? 1You have selected Linuxrootlocalhost shell.example#Case esac语句：格式：案例：rootlocalhost shell.example# vi select.case #!/bin/bash# select case Usageecho a is 5, b is 3. Please select you method: a=5b=3select var in a+b a-b a*b a/bdo breakdonecase $var in a+b) echo a+b=expr $a + $b; a-b) echo a-b=expr $a - $b; a*b) echo a*b=expr $a * $b; a/b) echo a/b=expr $a / $b; *) echo input error.esacrootlocalhost shell.example# sh select.case a is 5, b is 3. Please select you method: 1) a+b2) a-b3) a*b4) a/b#? 2a-b=2rootlocalhost shell.example#While语句：格式：、案例：rootlocalhost shell.example# vi while#!/bin/shnum=1while $num -le 10 do SUM=expr $num * $num echo $SUM num=expr $num + 1donerootlocalhost shell.example# sh while 149162536496481100rootlocalhost shell.example#Until语句：格式：案例：rootlocalhost shell.example# vi until #!/bin/shuntil -x /etc/inittab do /bin/ls -l /etc/inittab exit 0donerootlocalhost shell.example# sh until -rw-r-r- 1 jack sys 1668 May 22 16:05 /etc/inittabrootlocalhost shell.example#跳出循环：break和continueShift 指令：范例：rootlocalhost shell.example# vi shift #!/bin/shif $# -le 0 then echo Not enough parameters exit 0fisum=0while $# -gt 0 do sum=expr $sum + $1 shiftdoneecho $sumrootlocalhost shell.example# sh shift Not enough parameters函数应用：函数的定义：函数中的变量：范例：rootlocalhost shell.example# vi function HELP()echo Usage: sh function $1 $2 $3if $# -ne 3 then HELP /调用函数else echo thank for your input, the three arguments is 1 2 3. fishell脚本调试：Awk命令应用：作用：分段提取格式：awk F 域分隔符 命令案例：自动生成系统信息rootlocalhost shell.example# vi sysinfo.sh #!/bin/sh# auto mail for system info/bin/date +%F /tmp/sysinfo 时间echo disk info: /tmp/sysinfo 磁盘信息/bin/df -h /tmp/sysinfoecho /tmp/sysinfoecho online users: /tmp/sysinfo 在线用户信息/usr/bin/who | /bin/grep -v root /tmp/sysinfoecho /tmp/sysinfoecho memory info: /tmp/sysinfo 内存信息/usr/bin/free -m /tmp/sysinfoecho /tmp/sysinfo# write root/usr/bin/write root /tmp/temp.pidkillid=cat /tmp/temp.pidfor PID in $killiddo /bin/kill -9 $PID 2 /dev/nulldonerootlocalhost shell.example# sh killuser.sh zhuangqlKilledrootlocalhost shell.example#案例：批量添加用户rootlocalhost shell.example# vi useradd.sh #!/bin/sh# Author: Sam # The script to add user# /etc/passwd infoecho please input username:read name /用户名前缀echo please input number:read numn=1while $n -le $num do /usr/sbin/useradd $name$n /创建用户名 n=expr $n + 1 /命令替换符done# /etc/shadow infoecho please input the password:read passwdm=1while $m -le $num do echo $passwd | /usr/bin/passwd -stdin $name$m /设置密码 m=expr $m + 1done# dos2unix scriptrootlocalhost shell.example# sh useradd.sh please input username:userplease input number:10please input the password:111111 Changing password for user user1.passwd: all authentication tokens updated successfully.Changing password for user user2.passwd: all authentication tokens updated successfully.Changing password for user user3.passwd: all authentication tokens updated successfully.Changing password for user user4.passwd: all authentication tokens updated successfully.Changing password for user user5.passwd: all authentication tokens updated successfully.Changing password for user user6.passwd: all authentication tokens updated successfully.Changing password for user user7.passwd: all authentication tokens updated successfully.Changing password for user user8.passwd: all authentication tokens updated successfully.Changing password for user user9.passwd: all authentication tokens updated successfully.Changing password for user user10.passwd: all authentication tokens updated successfully.rootlocalhost shell.example#案例：删除用户rootlocalhost shell.example# vi deluser.sh #!/bin/shecho please input username:read name /用户前缀echo please input number:read num/用户数量sum=0while $sum -lt $num dosum=expr $sum + 1/usr/sbin/userdel -r $name$sumDonerootlocalhost shell.example# sh deluser.sh please input username:userplease input number:5案例：显示用户信息rootlocalhost shell.example# vi userinfo.sh #!/bin/sh# display users info./bin/echo Please input the usernameread username/bin/grep $username /etc/passwd /dev/null 2 /dev/nullif $? -eq 0 then /bin/echo username is : $usernameelse /bin/echo user $username does not exist exit 1fi/bin/echo#