linux shell 小技能

环境：

[root@test ~]# cat /etc/redhat-release 
CentOS release 6.5 (Final)
[root@test ~]# uname -a
Linux test 2.6.32-431.el6.x86_64 #1 SMP Fri Nov 22 03:15:09 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux

一、shell 多行注释

[root@test tmp]# cat test.sh 
#!/usr/bin/env bash
#

echo 1
echo 2
echo 3
echo 4
echo 5
echo 6
echo 7
[root@test tmp]# sh test.sh 
1
2
3
4
5
6
7
[root@test tmp]# vim test.sh 
[root@test tmp]# cat test.sh
#!/usr/bin/env bash
#

echo 1
echo 2
:<<!
echo 3
echo 4
echo 5
echo 6
!
echo 7
[root@test tmp]# sh test.sh 
1
2
7

提示：这里的叹号(！)可以换成其他任意成对的字符

二、内置的模糊匹配 

 　　注意：使用匹配的方式一定要是[[ ]]这种方式

　　1、正则方式匹配

[root@test ~]# [[ "$var" =~ "a|b" ]] && echo ok || echo fail
fail
[root@test ~]# [[ "$var" =~ a|b ]] && echo ok || echo fail
ok
[root@test ~]# var=1564
[root@test ~]# [[ "$var" =~ a|b ]] && echo ok || echo fail
fail
[root@test ~]# var=b
[root@test ~]# [[ "$var" =~ a|b ]] && echo ok || echo fail
ok
[root@test ~]# ip=172.16.100.5
[root@test ~]# [[ "$ip" =~ ^([0-9]{1,3}.){3}[0-9]{1,3}$ ]] && echo ok || echo fail
ok
[root@test ~]# [[ "$ip" =~ "^([0-9]{1,3}.){3}[0-9]{1,3}$" ]] && echo ok || echo fail
fail
[root@test ~]# reg='^([0-9]{1,3}.){3}[0-9]{1,3}$'
[root@test ~]# [[ "$ip" =~ $reg ]] && echo ok || echo fail
ok
[root@test ~]# [[ "$ip" =~ "$reg" ]] && echo ok || echo fail
fail

[root@test ~]# a=uuoipwsdf23423rf5
[root@test ~]# [[ $a =~ .*df.* ]] && echo ok || echo fail
ok
[root@test ~]# [[ $a =~ .*hh.* ]] && echo ok || echo fail
fail

小结：通过上面的示例，可以看出被匹配的对象不能加双引号，就算是变量也不能加。

　　2、使用通配模式匹配

[root@test ~]# a=bbccddee
[root@test ~]# [[ $a = *e ]] && echo ok || echo fail
ok
[root@test ~]# [[ $a = *f ]] && echo ok || echo fail
fail
[root@test ~]# [[ $a = bb*ee ]] && echo ok || echo fail
ok
[root@test ~]# [[ $a = cc*ee ]] && echo ok || echo fail
fail
[root@test ~]# [[ $a = *cc*ee ]] && echo ok || echo fail
ok
[root@test ~]# [[ $a = *dd ]] && echo ok || echo fail
fail
[root@test ~]# [[ $a = *dd* ]] && echo ok || echo fail
ok
[root@test ~]# a=123
[root@test ~]# [[ $a = 1 ]] && echo ok || echo fail
fail
[root@test ~]# [[ $a = 1* ]] && echo ok || echo fail
ok
[root@test ~]# [[ $a = *1* ]] && echo ok || echo fail
ok
[root@test ~]# [[ $a = [0-9] ]] && echo ok || echo fail
fail
[root@test ~]# [[ $a = [0-9][0-9][0-9] ]] && echo ok || echo fail
ok
[root@test ~]# [[ $a = [a-z][a-z][a-z] ]] && echo ok || echo fail
fail
[root@test ~]# a=9
[root@test ~]# [[ $a = [a-z] ]] && echo ok || echo fail
fail

应用场景：可以用作对用户从命令行传递给脚本的参数做合法验证

三、case语句模糊匹配（通配符）

[root@test tmp]# cat test.sh 
#!/usr/bin/env bash
#
test(){
case $1 in
    *abc*)
        echo yes
        ;;
    *)
        echo no
        ;;
esac
}

#test hkfase2abcljfp
test $1

[root@test tmp]# sh test.sh fasdfasdf
no
[root@test tmp]# sh test.sh qewfsdabchwerf
yes

尝试用正则模式匹配
[root@test tmp]# cat test.sh 
#!/usr/bin/env bash
#
test(){
case $1 in
    ^.*abc.*$)
        echo yes
        ;;
    *)
        echo no
        ;;
esac
}

#test hkfase2abcljfp
test $1

[root@test tmp]# sh test.sh qewfsdabchwerf
no

四、trap型号捕捉

[root@test tmp]# cat test.sh
#!/usr/bin/env bash
#

fun_exit(){
    echo -ne "
The program receives an interrupt signal,Do you wish to really exit? Your choice [ y | n ]: "
    read answer
    case $answer in
        y)
           exit 1
           ;;
        n)
           echo "program continue ..."
           ;;
        *)
           echo 'continue ...'
           ;;
    esac
}

trap "fun_exit" 1 2 3 15

while true;do
    echo 1
    sleep 2
done
[root@test tmp]# sh test.sh 
1
1
1
^C
The program receives an interrupt signal,Do you wish to really exit? Your choice [ y | n ]: n
program continue ...
1
1
1
^C
The program receives an interrupt signal,Do you wish to really exit? Your choice [ y | n ]: 
continue ...
1
1
^C
The program receives an interrupt signal,Do you wish to really exit? Your choice [ y | n ]: y
[root@test tmp]# 

提示：如果连续多次按ctrl+c 还是会中断