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unix测试何时在测试命令中使用eq vs = vs ==？

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unix测试何时在测试命令中使用eq vs = vs ==？

我什么时候应该使用-eqvs =vs==

例如

[[ $num -eq 0 ]]

[[ $num = 'zzz' ]]

-eq我观察到使用(and-ne等) 表示数字和=字符串的模式。这有什么原因吗？我应该什么时候使用==

答案1

因为那是这些操作数的定义。从POSIX 测试文档，OPERANDS 部分:

s1 = s2

如果字符串 s1 和 s2 相同，则为 True；否则为假。

...

n1-eq n2

如果整数 n1 和 n2 在代数上相等，则为 True；否则为假。

==不是由 POSIX 定义的，它是 的扩展bash，源自ksh.==当您想要便携性时不应该使用。从bash 文档 - Bash 条件表达式:

字符串1 == 字符串2

字符串1 = 字符串2

如果字符串相等则为 True。'=' 应与测试命令一起使用以确保 POSIX 一致性。

答案2

符号=用于字符串比较，而-eq用于整数比较。两者都与test和 一起工作[...]。如果您将bashthen 与语法一起使用[[...]]，您也可以将其用于==字符串比较。另外，在 bash=和==with中也[[...]]适用patterns（例如[[ $x == y* ]].

答案3

以下序列可以提供更详细的
帮助：

gnu:~$ [ sam -eq sam ]  
bash: [: sam: integer expression expected  
gnu:~$ echo "Exit status of \"[ sam -eq sam ]\" is $?."  
Exit status of "[ sam -eq sam ]" is 2.  

gnu:~$ [ 5 -eq 5 ]  
gnu:~$ echo "Exit status of \"[ 5 -eq 5 ]\" is $?."  
Exit status of "[ 5 -eq 5 ]" is 0.  

gnu:~$ [ 5 = 5 ]  
gnu:~$ echo "Exit status of \"[ 5 = 5 ]\" is $?."  
Exit status of "[ 5 = 5 ]" is 0.  

gnu:~$ [ sam = sam ]  
gnu:~$ echo "Exit status of \"[ sam = sam ]\" is $?."  
Exit status of "[ sam = sam ]" is 0.  

gnu:~$ [ 5 == 5 ]  
gnu:~$ echo "Exit status of \"[ 5 == 5 ]\" is $?."  
Exit status of "[ 5 == 5 ]" is 0.  

gnu:~$ [ sam == sam ]  
gnu:~$ echo "Exit status of \"[ sam == sam ]\" is $?."  
Exit status of "[ sam == sam ]" is 0.  

gnu:~$ (( 5 == 5 ))  
gnu:~$ echo "Exit status of \"(( 5 == 5 ))\" is $?."  
Exit status of "(( 5 == 5 ))" is 0.  

gnu:~$ (( sam == sam ))  
gnu:~$ echo "Exit status of \"(( sam == sam ))\" is $?."  
Exit status of "(( sam == sam ))" is 0.  

gnu:~$ ( sam = sam )  
The program 'sam' is currently not installed. You can install it by typing:  
sudo apt-get install simon  
gnu:~$ echo "Exit status of \"( sam = sam )\" is $?."  
Exit status of "( sam = sam )" is 127.  

gnu:~$ ( 5 = 5 )  
5: command not found  
gnu:~$ echo "Exit status of \"( 5 = 5 )\" is $?."  
Exit status of "( 5 = 5 )" is 127.  

gnu:~$ ( sam == sam )  
The program 'sam' is currently not installed. You can install it by typing:  
sudo apt-get install simon  
gnu:~$ echo "Exit status of \"( sam == sam )\" is $?."  
Exit status of "( sam == sam )" is 127.  

gnu:~$ ( 5 == 5 )  
5: command not found  
gnu:~$ echo "Exit status of \"( 5 == 5 )\" is $?."  
Exit status of "( 5 == 5 )" is 127.

答案4

从man test：

-eq， ETC。

接力算术测试。参数必须完全是数字（可能是负数），或者是特殊表达式“-l STRING”，其计算结果为 STRING 的长度。

STRING1 = STRING2

 True if the strings are equal.

STRING1 == STRING2

 True if the strings are equal (synonym for =).

所以=和==是同义词

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