linux基础之Shell Script入门介绍
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2023-11-28 14:47:10
linux基础之shell script
1 shell scipt使用指令和基本程序设计结构写成的程序，可以完成复杂的处理流程
1.1 程序书写
复制代码 代码如下...
linux基础之shell script
1 shell scipt
使用指令和基本程序设计结构写成的程序，可以完成复杂的处理流程
1.1 程序书写
复制代码 代码如下:
#!/bin/bash
# program:
# this program shows "hello wrold" in your screen.
# history:
# 2013/2/3 on_1y first release
path=$path
export path
echo -e "hello world!\a\n"
exit 0
第一行 #!/bin/bash 说明使用的shell类型,不同shell语法可能不同，所以要说明使用的是哪种shell
其它#开始的表示注释,注释一般需要说明
程序功能
版本历史
作者及联系方式
设置好path变量，以便直接可以调用相应路径下的命令
程序主体部分
exit 0 表示程序执行成功，向环境返回0
1.2 程序执行
bash $bash sh01.sh #如果用sh sh01.sh而sh又不是指向bash，那么sh01.sh内的语法就会不一致，因为用 #sh去解释了bash语法写的shell script,针对这个程序，如果 #$type sh #得到sh is hashed (/bin/sh) #那么会输出-e hello world!,而非hello world!
复制代码 代码如下:
$./xxx.sh $chmod +x sh01.sh $./sh01.sh
source $ source sh01.sh
注：用bash和用source的不同在于，用bash执行时，shell script其实是在在父程序bash下新建了一个 bash子程序，这个子程序中执行，当程序执行完后，shell script里定义的变量都会随子程序的结束而消失， 而用source执行时，是在父程序bash中执行,shell script里定义的变量都还在。
2 简单shell练习
2.1 例1 接收用户输入
复制代码 代码如下:
# !/bin/bash
# program:
# this program is used to read user's input
# site: www.jb51.net
# 2013/2/3 on_1y first release
path=$path
export path
read -p "your first name:" firstname # tell user to input
read -p "your last name:" lastname # tell user to input
echo -e "\nyour full name: $firstname $lastname"
exit 0
调用：
复制代码 代码如下:
$ bash sh02.sh
your first name:minix
your last name:007
your full name: minix 007
2.2 例2 按日期建立相似名字的文件
复制代码 代码如下:
# !/bin/bash
# program:
# this program is used to create files according to date
# history:
# 2013/2/3 on_1y first release
path=$path
export path
# get filename from user
echo -e "i will use 'touch' to create three files."
read -p "please input your filename:" tmpfilename
# prevent the user input [enter]
# check whether filename exists or not
filename=${tmpfilename:-"filename"}
# get the final filename according to date
date1=$(date --date='2 days ago' +%y%m%d) # date of 2 days ago
date2=$(date --date='1 days ago' +%y%m%d) # date of yesterday
date3=$(date +%y%m%d) # date of today
filename1=${filename}${date1}
filename2=${filename}${date2}
filename3=${filename}${date3}
# create file
touch "$filename1"
touch "$filename2"
touch "$filename3"
exit 0
调用：
复制代码 代码如下:
$ bash sh03.sh
i will use 'touch' to create three files.
please input your filename:whoknows
$ ls w*
whoknows20130201 whoknows20130202 whoknows20130203
3 判断式
3.1 测试文件是否存在
test -e filename会根据filename是否存在返回0或1,再交由echo显示结果：
复制代码 代码如下:
$ test -e sh01.sh && echo "exists" || echo "not exists"
exists
$ test -e sh0x.sh && echo "exists" || echo "not exists"
not exists
3.2 test常用选项
3.2.1 文件类型
复制代码 代码如下:
-e file :file是否存在
-f file :file是否存在且为文件
-d file :file是否存在且为目录
3.2.2 权限
-r file :file是否有读的权限
3.2.3 文件新旧比较
-nt file1 file2 : file1 是否比 file2新
3.2.4 整数，字符串，多重条件判断
-z string: string是否为空
例：输出指定文件类型及属性
复制代码 代码如下:
# !/bin/bash
# program:
# this program is used to output type and permission of the target file
# history:
# 2013/2/3 on_1y first release
path=$path
export path
# get filename from user
echo -e "input name of the file that you want to check.\n"
read -p "filename:" filename
test -z $filename && echo "you must input a filename." && exit 0
# check whether the file exists or not
test ! -e $filename && echo "the file '$filename' do not exists" && exit 0
# check type and permission of the file
test -f $filename && filetype="regular file"
test -d $filename && filetype="directory"
test -r $filename && perm="readable"
test -w $filename && perm="$perm writable"
test -x $filename && perm="$perm executable"
# output result
echo "the filename:$filename is a $filetype"
echo "and permissions are :$perm"
exit 0
调用：
复制代码 代码如下:
$ bash sh04.sh
input name of the file that you want to check.
filename:sh01.sh
the filename:sh01.sh is a regular file
and permissions are :readable writable executable
3.3 使用[]判断
测试文件是否存在
复制代码 代码如下:
$ [ -e "sh01.sh" ] ; echo $?
0
$ [ -e "sh0x.sh" ] ; echo $?
1
注意[]内空格必须有
这种方法和test的test -e "sho1.sh" ; echo $? 是一致的
4 shell script 参数
复制代码 代码如下:
# !/bin/bash
# program:
# this program is used to ouput parameter of the shell script
# history:
# 2013/2/3 on_1y first release
path=$path
export path
echo "the script's name is ==> $0"
echo "total parameter number is ==> $#"
# check whether number of the parameter is less than 2
[ "$#" -lt 2 ] && echo "the number of parameter is less than 2.stop here." && exit 0
echo "the whole parameter is ==> '$@'"
echo "the first parameter is ==> $1"
echo "the first parameter is ==> $2"
exit 0
调用：
复制代码 代码如下:
$ bash sh05.sh 1a 2b 3c 4d
the script's name is ==> sh05.sh
total parameter number is ==> 4
the whole parameter is ==> '1a 2b 3c 4d'
the first parameter is ==> 1a
the first parameter is ==> 2b
注：从以上程序可以看出与参数有关的预设变量如何表示
5 条件表达式
5.1 if 结构
复制代码 代码如下:
# !/bin/bash
# program:
# this program is used to show if else expression
# history:
# 2013/2/3 on_1y first release
path=$path
export path
read -p "please input [y/n]" choice
if [ "$choice" == "y" ] || [ "$choice" == "y" ];then
echo "ok, continue"
exit 0
fi
if [ "$choice" == "n" ] || [ "$choice" == "n" ];then
echo "oh, interupt"
exit 0
fi
exit 0
调用：
复制代码 代码如下:
$ bash sh06.sh
please input [y/n]y
ok, continue
$ bash sh06.sh
please input [y/n]n
oh, interupt
5.2 if else 结构
复制代码 代码如下:
# !/bin/bash
# program:
# this program is used to show if else expression
# history:
# 2013/2/3 on_1y first release
path=$path
export path
read -p "please input [y/n]" choice
if [ "$choice" == "y" ] || [ "$choice" == "y" ];then
echo "ok, continue"
exit 0
elif [ "$choice" == "n" ] || [ "$choice" == "n" ];then
echo "oh, interupt"
exit 0
else
echo "input [y/n]"
fi
exit 0
5.3 case
复制代码 代码如下:
# !/bin/bash
# program:
# this program is used to show case expression
# history:
# 2013/2/3 on_1y first release
path=$path
export path
read -p "tell me your choice:[1-3]=>" choice
case $choice in
"1")
echo "your choice is one"
"2")
echo "your choice is two"
"3")
echo "your choice is three"
esac
exit 0
调用：
复制代码 代码如下:
$ bash sh08.sh
tell me your choice:[1-3]=>2
your choice is two
$ bash sh08.sh
tell me your choice:[1-3]=>1
your choice is one
$ bash sh08.sh
tell me your choice:[1-3]=>3
your choice is three
6 函数
复制代码 代码如下:
# !/bin/bash
# program:
# this program is used to test function
# history:
# 2013/2/3 on_1y first release
path=$path
export path
function myprint(){
echo -n "your choice is "
}
read -p "tell me your choice:[1-3]=>" choice
case $choice in
"1")
myprint;echo "one"
"2")
myprint;echo "two"
"3")
myprint;echo "three"
esac
exit 0
调用：
复制代码 代码如下:
$ bash sh09.sh
tell me your choice:[1-3]=>1
your choice is one
$ bash sh09.sh
tell me your choice:[1-3]=>2
your choice is two
$ bash sh09.sh
tell me your choice:[1-3]=>3
your choice is three
7 循环
7.1 while
复制代码 代码如下:
# !/bin/bash
# program:
# this program shows while expression
# history:
# 2013/2/3 on_1y first release
path=$path
export path
while [ "$choice" != "yes" ]
do
read -p "give your choice [yes/no]:" choice
done
exit 0
调用：
复制代码 代码如下:
$ bash sh10.sh
give your choice [yes/no]:no
give your choice [yes/no]:no
give your choice [yes/no]:nx
give your choice [yes/no]:yes
7.2 for
复制代码 代码如下:
# !/bin/bash
# program:
# this program is used to demo for expression
# history:
# 2013/2/3 on_1y first release
path=$path
export path
for choice in 1 2 3
do
echo "your choice is $choice"
done
exit 0
调用示例：
复制代码 代码如下:
$ bash sh11.sh
your choice is 1
your choice is 2
your choice is 3
8 shell script的追踪与debug
sh -n xx.sh # 语法检查
sh -x xx.sh # 列出xx.sh的执行过程