Shell学习之整数和字符串的比较

1、二元比较操作符

1.1、整数比较

-eq   等于 如：if [ “$a” -eq “$b” ]

-ne   不等于 如：if [ “$a” -ne “$b” ]

-gt   大于 如：if [ “$a” -gt “$b” ]

-ge   大于或等于 如：if [ “$a” -ge “$b” ]

-lt   小于或等于 如：if [ “$a” -lt “$b”]

 

实例：

#!/bin/bash

a=8

b=10

 

##

if [ "${a}" -eq "${b}" ];then

printf "$a is equal $b\n"

else

printf "$a is not equal $b \n"

fi

 

##

if [ "${a}" -gt "${b}" ];then

printf "$a is great than $b\n"

else

printf "$a is not great than $b\n"

fi

执行结果：

tay@tay:/mnt/hgfs/hzs/shell$ ./if.sh

8 is not equal 10

8 is not great than 10

 

 

1.2、字符串的比较

= 等于 如：if [ “$a” = “$b” ]

== 等于 如：if [ “$a” == “$b” ],与=等价

 

例子：

#!/bin/bash

 

_STRING_A_="this is string a"

_STRING_B_="this is string b"

 

if [ "${_STRING_A_}" = "${_STRING_B_}" ];then

printf "_STRING_A_ is equal _STRING_B_\n"

else

printf "_STRING_A_ is not equal _STRING_B_\n"

fi

 

if [ "${_STRING_A_}" == "${_STRING_B_}" ];then

printf "_STRING_A_ is equal _STRING_B_\n"

else

printf "_STRING_A_ is not equal _STRING_B_\n"

fi

 

执行结果：

tay@tay:/mnt/hgfs/hzs/shell$ ./string_compare.sh

_STRING_A_ is not equal _STRING_B_

_STRING_A_ is not equal _STRING_B_

 

 

 

关键点：括号两边各有一个空格，这是unix shelll的要求