- shell程序介绍
1.查看我们的Linux（centos6.5为例）有多少我们可以使用的shell：
[root@localhost bin]# cat /etc/shells
/bin/sh
/bin/bash
/sbin/nologin
/bin/dash
/bin/tcsh
/bin/csh
系统某些服务在运作过程中，会去检查使用者能够使用的shells，而这些shell的查询就是由/etc/shells这个档案。
2.当我们登入Linux系统的时候，系统就会给我一个shell来工作，而这个登录取得的shell就记录在/etc/passwd这个档案里:
[root@localhost bin]# cat /etc/passwd
root:x:::root:/root:/bin/bash
bin:x:::bin:/bin:/sbin/nologin
daemon:x:::daemon:/sbin:/sbin/nologin
adm:x:::adm:/var/adm:/sbin/nologin
...
3.shell的内部指令type，查看指令来自外部指令还是内建在bash当中。
[root@localhost bin]# man cd
[root@localhost bin]# type cd
cd is a shell builtin
[root@localhost bin]# type -t cd
builtin #表示该指令为bash内建的指令功能
[root@localhost bin]# type -a cd
cd is a shell builtin
[root@localhost bin]# type type
type is a shell builtin
[root@localhost bin]# type it ls
alias #表示该指令为命名别名所设定的名称
[root@localhost bin]# type uname
uname is hashed (/bin/uname)
[root@localhost bin]# type -t uname
file #表示为外部指令
4.变量的取用 echo
[root@localhost bin]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin
[root@localhost bin]# echo ${PATH}
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin
变量的设定 = ，如果一个变量未设定，内容为空
[root@localhost bin]# echo $myname [root@localhost bin]# myname=tian
[root@localhost bin]# echo $myname
tian
子程序，就是在目前这个shell的情况下，去启用另一个新的shell，新的shell就是子程序。在一般状态下，父程序的自定义变量无法在子程序内使用，但是通过export将变量变成环境变量，就能在子程序下应用了。
[root@localhost bin]# echo $name
yes
[root@localhost bin]# bash #进入所谓的子程序
[root@localhost bin]# echo $name [root@localhost bin]# exit #离开子程序
exit
[root@localhost bin]# export name
[root@localhost bin]# bash
[root@localhost bin]# echo $name
yes
[root@localhost bin]# exit
5.变量的设定规则：
6.环境变量
env，environment的简写，列出所有的环境变量
[root@localhost /]# env
HOSTNAME=localhost.localdomain
SHELL=/bin/bash
TERM=xterm
HISTSIZE=
USER=root
...
set，观察所有变量（包含环境变量和自定义变量）
[root@localhost /]# set
BASH=/bin/bash
BASH_VERSINFO=([]="" []="" []="" []="" []="release" []="i386-redhat-linux-gnu")
BASH_VERSION='4.1.2(1)-release'
HISTFILE=/root/.bash_history
HISTFILESIZE=
HISTSIZE=
HOSTTYPE=i386
OLDPWD=/
OSTYPE=linux-gnu
PPID=
PS1='[\u@\h \W]\$ '
...
PS1：提示字符的设定
[root@localhost php]# PS1='[\u@\h \w]\$'
[root@localhost /usr/local/php]#ls
$变量，代表的是目前这个shell的线程代号，即PID（Process ID）
[root@localhost /]#echo $$
?变量：上一个执行的指令所回传的值，如果执行成功，则回传一个0值，否则，就会回传错误代码（一般为非0值）
[root@localhost scripts]# ls
sh01.sh sh02-.sh sh02.sh sh03.sh sh04.sh
[root@localhost scripts]# echo $?
7.数据流重导向
数据流重导向可以将standard output与standard error output分别传送到其他档案或装置去，而分别传送所用的特殊字符则如下所示：
[tianxintian22@localhost ~]$ find /home -name .bashrc
find: `/home/w002': Permission denied <==Standard error
/home/tianxintian22/.bashrc <==Standard output
find: `/home/w001': Permission denied <==Standard error
#将stdout与stderr分别存到不同的档案
[tianxintian22@localhost ~]$ find /home -name .bashrc > list_right > list_error
[tianxintian22@localhost ~]$ ls
Desktop Documents Downloads list_error list_right Music Pictures Public Templates Videos
#将错误数据丢弃，屏幕显示正确的数据
#/dev/null 垃圾桶黑暗装置，可以吃掉任何导向这个装置的信息
[tianxintian22@localhost ~]$ find /home -name .bashrc > /dev/null
/home/tianxintian22/.bashrc
#将指令的数据全部写入list档案中
[tianxintian22@localhost ~]$ find /home -name .bashrc > list >&
#[tianxintian22@localhost ~]$ find /home -name .bashrc &> list 这句等同于上一句
[tianxintian22@localhost ~]$ ls
Desktop Documents Downloads list list_error list_right Music Pictures Public Templates Videos
[tianxintian22@localhost ~]$ cat list
find: `/home/w002': Permission denied
/home/tianxintian22/.bashrc
find: `/home/w001': Permission denied
- shell script
1.路径与指令搜寻顺序
2.script指令下达
以上方式下达脚本时，script都会使用一个新的bash环境来执行脚本内的指令，也就是说，script是在子程序的bash内执行的。
3.指令依序执行关系
#不清楚/tmp/abc是否存在，但是要建立/tmp/abc/hehe档案
[root@localhost ~]ls /tmp/abc || mkdir /tmp/abc && touch /tmp/abc/hehe
4.test指令的测试功能
[root@localhost scripts]# ls
sh01.sh sh02-.sh sh02.sh sh03.sh sh04.sh
[root@localhost scripts]# test -e sh01.sh #该档名是否存在
[root@localhost scripts]# echo $? [root@localhost scripts]# test -f sh01.sh #该档名是否存在且为档案（file）
[root@localhost scripts]# echo $? [root@localhost scripts]# test -d sh01.sh #该文件名是否存在且为目录
[root@localhost scripts]# echo $? [root@localhost scripts]# test -d ~/scripts
[root@localhost scripts]# echo $?
5.判断符号[ ]
编写脚本：sh01.sh
[root@localhost scripts]# vim sh01.sh
#!/bin/bash
#Program
# This program shows the user's choice
#History
#// tianxintian22 first release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH
read -p "Please input (Y/N)" choice
[ "$choice" == 'Y' -o "$choice" == 'y' ] && echo "OK,continue" && exit 0 # -o 等价于或者（or）
[ "$choice" == 'n' -o "$choice" == 'N' ] && echo "Oh,interrupt" && exit
echo "I don't know what your choice is" && exit
执行脚本：
[root@localhost scripts]# sh sh01.sh
Please input (Y/N)Y
OK,continue
6.shell script 默认变数（$1,$2...）
[root@localhost scripts]# vim sh02.sh
#!/bin/bash
#program
# program shows the script name, parameters...
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH
echo "The script name is ==> $0"
echo "Total parameter number is ==> $#"
[ "$#" -lt ] && echo "The number of parameter is less than 2.Stop here." && exit
echo "Your whole parameter is ==>'$@'"
echo "The first parameter is ==>$1"
echo "The second parameter is ==>$2"
exit
执行脚本：
[root@localhost scripts]# ./sh02.sh
The script name is ==> ./sh02.sh
Total parameter number is ==>
The number of parameter is less than .Stop here.
[root@localhost scripts]# ./sh07.sh one two
The script name is ==> ./sh02.sh
Total parameter number is ==>
Your whole parameter is ==>'one two'
The first parameter is ==>one
The second parameter is ==>two
7.条件判断式 if...then
[root@localhost scripts]# vim sh01-.sh
#!/bin/bash
#Program
# This program shows the user's choice
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH
read -p "Please input (Y/N):" choice
if [ "$choice" == 'Y' ] || [ "$choice" == 'y' ];then
echo "OK,continue"
elif [ "$choice" == 'n' ] || [ "$choice" == 'N' ];then
echo "Oh,interrupt"
else
echo "I don't know what your choice is"
fi
执行脚本：
[root@localhost scripts]# ./sh01-.sh
Please input (Y/N):n
Oh,interrupt
8.case...esac 判断
[root@localhost scripts]# vim sh02.sh
#!/bin/bash
#program
# Show "hello" from $ by using case...esac
#history
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH
case $ in
"hello")
echo "Hello,how are you?"
;;
"")
echo "You must input parameter, ex> {$0 someword}"
;;
*)
echo "Usage $0 {hello}"
;;
esac
执行脚本：
[root@localhost scripts]# ./sh02.sh hello
Hello,how are you?
[root@localhost scripts]# ./sh02.sh test
Usage ./sh02.sh {hello}
[root@localhost scripts]# ./sh02.sh
You must input parameter, ex> {./sh02.sh someword}
9.function功能
[root@localhost scripts]# vim sh02-.sh
#!/bin/bash
#program
# use function to repeat information
#history
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH
function printit(){
echo -n "Your choice is "
}
echo "This program will print your selection!"
case $ in
"one")
printit;echo $ | tr 'a-z' 'A-Z'
;;
"two")
printit;echo $ | tr 'a-z' 'A-Z'
;;
"three")
printit;echo $ | tr 'a-z' 'A-Z'
;;
*)
echo "Usage $0 {one|two|three}"
;;
esac
执行脚本：
[root@localhost scripts]# ./sh02-.sh
This program will print your selection!
Usage ./sh02-.sh {one|two|three}
[root@localhost scripts]# ./sh02-.sh one
This program will print your selection!
Your choice is ONE
shell script 的执行方式是由上而下，由左而右，因此在shell script当中的设定一定要写在程序的最前面！
[root@localhost scripts]# vim sh02-.sh
#!/bin/bash
#program
# use function to repeat information
#history
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH
function printit(){
echo "Your choice is $1"
}
echo "This program will print your selection!"
case $ in
"one")
printit
;;
"two")
printit
;;
"three")
printit
;;
*)
echo "Usage $0 {one|two|three}"
;;
esac
执行脚本：
[root@localhost scripts]# ./sh02-.sh
This program will print your selection!
Usage ./sh02-.sh {one|two|three}
[root@localhost scripts]# ./sh02-.sh one
This program will print your selection!
Your choice is
10.while do done;until do done
#当condition条件满足时，就进行循环
while [ condition ]
do
程序语句
done
#当condition条件成立时，终止循环
until [ condition ]
do
程序语句
done
计算1+2+3+4+...+100：
#!/bin/bash
#program calculate '1+2+3+4+...+100'
#history ...
sum=
i=
while [ "$i" != '' ]
do
i=$(($i+))
sum=$(($sum+$i))
done
echo "1+2+3+...+100="$sum
#!/bin/bash
#program calculate '1+2+3+4+...+100'
#history
sum=
i=
until [ "$i" == '' ]
do
i=$(($i+))
sum=$(($sum+$i))
done
echo "1+2+3+...+100="$sum
11.for do done(固定循环)
for var in con1 con2 con3 ...
do
程序段
done
$var 的变量内容在循环时：第一次循环时，$var的内容为con1；第二次循环时，$var的内容为con2；第三次循环时，$var内容为con3；...
eg1:
#!/bin/bash
#program
# using for ... loop to print animals
#history
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH
for animal in dog cat elephant
do
echo "There are ${animal}s..."
done
执行脚本：
[root@localhost scripts]# sh sh04.sh
There are dogs...
There are cats...
There are elephants...
eg2:
#!/bin/bash
users=$(cut -d ':' -f /etc/passwd)
for user in $users
do
id $user
done
执行脚本：
[root@localhost scripts]# sh sh05.sh
uid=(root) gid=(root) groups=(root)
uid=(bin) gid=(bin) groups=(bin),(daemon),(sys)
uid=(daemon) gid=(daemon) groups=(daemon),(bin),(adm),(lp)
uid=(adm) gid=(adm) groups=(adm)
...
12.for...do...done
for((初始值;限制值;执行步阶))
do
程序段
done
[root@localhost scripts]# cat sh06.sh
#!/bin/bash
#program
# try do calculate +++...+${your_input}
#history
read -p "input a number:" number
sum=
for((i=;i<=number;i++))
do
sum=$(($sum+$i))
done
echo "1+2+3+...+$number="$sum
执行脚本：
[root@localhost scripts]# sh sh06.sh
input a number:
+++...+=
13.debug
[root@localhost scripts]# sh -n sh06.sh
#如果语法没有问题，则不会显示任何信息 [root@localhost scripts]# sh -v sh06.sh #执行脚本前，现将脚本内容输出到屏幕上
#!/bin/bash
#program
# try do calculate +++...+${your_input}
#history
read -p "input a number:" number
input a number:
sum=
for((i=;i<=number;i++))
do
sum=$(($sum+$i))
done
echo "1+2+3+...+$number="$sum
+++...+= [root@localhost scripts]# sh -x sh06.sh #将使用到的script内容显示到屏幕上
+ read -p 'input a number:' number
input a number:
+ sum=
+ (( i= ))
+ (( i<=number ))
+ sum=
+ (( i++ ))
+ (( i<=number ))
+ sum=
+ (( i++ ))
+ (( i<=number ))
+ sum=
+ (( i++ ))
+ (( i<=number ))
+ sum=
+ (( i++ ))
+ (( i<=number ))
+ sum=
+ (( i++ ))
+ (( i<=number ))
+ echo +++...+=
+++...+=