10-4.shell编程.ppt

1、Linux Shell编程,函数,函数定义,在shell中还可以定义函数。函数实际上也是由若干条shell命令组成的，因此它与shell程序形式上是相似的，不同的是它不是一个单独的进程，而是shell程序的一部分。函数定义的基本格式为： function fname or fname 若干命令行 ,调用函数的格式为： fname param1 param2 shell函数可以完成某些例行的工作，而且还可以有自己的退出状态，因此函数也可以作为if、while等控制结构的条件。 在函数定义时不用带参数说明，但在调用函数时可以带有参数，此时shell将把这些参数分别赋予相应的位置参数$1、$2、.及

2、$*。,#!/bin/bashfunction fun1 echo this is the first functionfun1fun2() echo this is the second functionfun2 #bash test.sh this is the first functionthis is the second function,必须先定义，再调用,#!/bin/bashfunction fun1 echo this is the first functionfun1fun2fun2() echo this is the second function,函数名必须唯一,#!

3、/bin/bashfunction fun1 echo this is the first functionfun1fun1() echo this is the second functionfun1#bash test.sh this is the first functionthis is the second function,#!/bin/bash function hello () echo Hello,$1 today is date echo now going to the function hello hello kmust echo back from the funct

4、ion,#!/bin/bashfunction fun1 echo this is the first function ls -l xxfun1echo the exit status is :$? #bash test.sh this is the first functionls: xx: 没有那个文件或目录the exit status is :2 函数的退出状态为2，因为最后一条命令执行出错,#!/bin/bashfunction fun1 ls -l xx echo this is the first functionfun1echo the exit status is :$?

5、#bash test.sh ls: xx: 没有那个文件或目录this is the first functionthe exit status is :0 退出状态值却是0 ，因为最后一条命令执行无错,return命令可以使用单个整数值来定义函数退出状态,#!/bin/bashfunction fun1 read -p enter a value: value echo doubling the value return $ $value * 2 fun1echo the new value is $? #bash test.sh enter a value:24doubling the v

6、aluethe new value is 48,#!/bin/bashfname () read -p “please input a value:” valueecho $ $value * 2 result=fname#反引号echo the result is : $result#bash test.sh please input a value:13the result is : 26,函数参数,#!/bin/bashfunction fname if $# -eq 0 | $# -gt 2 then echo -1elif $# -eq 1 then echo $ $1 + $1 e

7、lse echo $ $1 * $2 fi,echo #1#echo -n adding 10 and 15 :value= fname 10 15echo $valueecho #2#echo -n adding just one num of 10:value= fname 10echo $valueecho #3#echo -n adding no num:value= fname echo $valueecho #4#echo -n adding three num 10 20 30 :value= fname 10 20 30echo $value,# bash test.sh #1

8、#adding 10 and 15 :150#2#adding just one num of 10:20#3#adding no num:-1#4#adding three num 10 20 30 :-1,#!/bin/bashfname () echo $ $1 + $2 if $# -eq 2 then value=fname #value=bad $1 $2 echo the result is : $valueelse echo please input two parametersfi #bash test.sh please input two parameters#bash

9、test.sh 1 2,全局变量,#!/bin/bashfun () value=$ $value * 2 read -p please input the value: value fun echo the new value is : $value,local-局部变量,#!/bin/bashfunction fun local temp=$ $value + 5 result=$ $temp + 2 temp=8value=10 fun echo the result is $resultif $temp -gt $value thenecho temp is largerelseech

10、o temp is smallerfi,创建库,funLib.sh function fun1 echo $ $1 + $2 function fun2 echo $ $1 * $2 test2.sh #!/bin/bash./funLib.shresult=fun1 12 24echo the result is $result,select,select 表达式是一种bash的扩展应用，尤其擅长于交互式使用。用户可以从一组不同的值中进行选择。 select var in . ; do break done,#!/bin/sh echo What is your favourite OS?

11、select var in Linux Gnu Hurd Free BSD Other; do break done echo You have selected $var,下面是该脚本运行的结果： What is your favourite OS? 1) Linux 2) Gnu Hurd 3) Free BSD 4) Other #1 You have selected Linux,#!/bin/bash ftype=file $1 case $ftype in $1: Zip archive*) unzip $1 ; $1: gzip compressed*) gunzip $1 ; $1: bzip2 compressed*) bunzip2 $1 ; *) error File $1 can not be uncompressed with smartzip; esac,#!/bin/bashPrintHelp() echo FORMAT: command arg echo