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Shell学习之条件测试(四)

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标签:string   ica   逻辑   install   script   数值   ||   文件   highlight   

Shell学习之条件测试

 

目录

逻辑测试

文件测试

数值比较

字符串比较

 

 

逻辑测试

格式:

  [ 表达式 ]  操作符 [ 表达式2 ] ……

  命令1  操作符  命令2 ……

常用的操作符 ( 注意:-a和-o放在[]里面用,&&和||放在[]外面用 )

    -a  或  &&           逻辑与

    -o  或 ||             逻辑或

      !               逻辑否

  


文件测试

文件测试

格式1:  [  操作符 文件或目录  ]  

格式2:test  操作符 文件或目录 

常用的测试操作符

    -d :测试是否为目录( Directory )

    -e :测试目录或文件是否存在(Exist)

    -f :测试是否为文件(File)

    -r :测试当前用户是否可读(read)

    -w:测试当前用户是否可写(write)

    -x :测试当前用户是否可执行(excute)

 

例子:备份Mysql数据库,业务代码没有完善

#/bin/bash
back_dir=/var/mysql_back

if !test -d $back_dir;then
	mkdir -p $back_dir
fi
echo "开始备份"

  

 


数值比较

格式1:[ 整数1 操作符 整数2 ]

格式2: test 整数1 操作符 整数2

常用的测试操作符

    -eq : 等于 (Equal)

    -ne : 不等于 (Not Equal)

    -gt : 大于(Greater Than)

    -lt : 小于 (Lesser Than)

    -le : 小于或等于(Lesser or Equal)

    -ge : 大于或等于(Greater or Equal)

  

例子

#/bin/bash
if [ $UID -ne 0];then
	echo "没有权限"
	exit
fi
yum -y install httpd

  

 

字符串比较

格式1:[ 字符串1 = 字符串2 ]

     [ 字符串1 != 字符串2 ]

格式2:[ -z 字符串 ]

常用的测试操作符

  = : 字符串内容相同

  != : 字符串内容不同

  -z : 字符串内容为空

  

例子

#/bin/bash
if [ $USER = "root"];then
	yum -y install httpd
fi
	echo "没有权限"
	exit

  

 

 

所有表达式

( EXPRESSION )
              EXPRESSION is true

       ! EXPRESSION
              EXPRESSION is false

       EXPRESSION1 -a EXPRESSION2
              both EXPRESSION1 and EXPRESSION2 are true

       EXPRESSION1 -o EXPRESSION2
              either EXPRESSION1 or EXPRESSION2 is true

       -n STRING
              the length of STRING is nonzero

       STRING equivalent to -n STRING

       -z STRING
              the length of STRING is zero

       STRING1 = STRING2
              the strings are equal

       STRING1 != STRING2
              the strings are not equal

       INTEGER1 -eq INTEGER2
              INTEGER1 is equal to INTEGER2

       INTEGER1 -ge INTEGER2
              INTEGER1 is greater than or equal to INTEGER2

       INTEGER1 -gt INTEGER2
              INTEGER1 is greater than INTEGER2

       INTEGER1 -le INTEGER2
              INTEGER1 is less than or equal to INTEGER2

       INTEGER1 -lt INTEGER2
              INTEGER1 is less than INTEGER2

       INTEGER1 -ne INTEGER2
              INTEGER1 is not equal to INTEGER2

       FILE1 -ef FILE2
              FILE1 and FILE2 have the same device and inode numbers

       FILE1 -nt FILE2
              FILE1 is newer (modification date) than FILE2

       FILE1 -ot FILE2
              FILE1 is older than FILE2

       -b FILE
              FILE exists and is block special

       -c FILE
              FILE exists and is character special

       -d FILE
              FILE exists and is a directory

       -e FILE
              FILE exists

       -f FILE
              FILE exists and is a regular file

       -g FILE
              FILE exists and is set-group-ID

       -G FILE
              FILE exists and is owned by the effective group ID

       -h FILE
              FILE exists and is a symbolic link (same as -L)

       -k FILE
              FILE exists and has its sticky bit set

       -L FILE
              FILE exists and is a symbolic link (same as -h)

       -O FILE
              FILE exists and is owned by the effective user ID

       -p FILE
              FILE exists and is a named pipe

       -r FILE
              FILE exists and read permission is granted

       -s FILE
              FILE exists and has a size greater than zero

       -S FILE
              FILE exists and is a socket

       -t FD  file descriptor FD is opened on a terminal

       -u FILE
              FILE exists and its set-user-ID bit is set

       -w FILE
              FILE exists and write permission is granted

       -x FILE
              FILE exists and execute (or search) permission is granted

  

 

Shell学习之条件测试(四)

标签:string   ica   逻辑   install   script   数值   ||   文件   highlight   

原文:https://www.cnblogs.com/-wenli/p/10367572.html

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