Three types of shell script condition judgment (Memo)

String comparison: Result

String1 = string2 string1 equals string2: True, otherwise false

String1! = String2 string1 equals to string2: false, otherwise true

-When n string is not equal to NULL: True, otherwise false

-Z string when string is null: true; otherwise, false

 

Arithmetic comparison result

Expression1-EQ expression2 expressions are equal: True, otherwise false

Expression1-ne expression2 expressions are not equal: True, otherwise false

When expression1-GT expression2 expression expression1 is greater than expression2: True, otherwise false

When the expression1-ge expression2 expression expression1 is greater than or equal to expression2: True, otherwise false

When expression1-lt expression2 expression expression1 is less than expression2: True, otherwise false

When the expression1-Le expression2 expression expression1 is less than or equal to expression2: True, otherwise false

! If expression is true, it is false.

 

File condition Result

-D When file is a directory: true; otherwise, false

-E file: true if file exists; otherwise, false. Note: historical reasons-e option is not portable. Therefore, use-F instead.

-F file exists: true; otherwise, false

-G file: true if the file is set by "Set-group-ID"; otherwise, false

-R file is readable: true; otherwise, false

-S file size is greater than 0: True, otherwise false

-U file is set to true by "Set-user-ID"; otherwise, false

-W file writable: true; otherwise, false

-X file is an executable file: true; otherwise, false