Conditional test in Shell

Condition test Type in Bash script: integer test

String test

File test

Expressions for conditional tests: [Expression]

[[expression]] expression must have a space before and after it

integer test :-eq: Tests whether two integers are equal and equal to True

-ne: Test whether two integers are unequal, not equal to True

-ge: Tests whether a number is greater than or equal to another number

-le: ..... ..... Less than or equal to ....

-gt: ..... ..... Greater than..........

-lt: ......... Less than..........

The logical relationship between commands (between statements) in bash:

Logic with: && The result of the previous command execution is false, the second statement is no longer executed

Logical OR: | |, the previous command executes the result is true, the second statement is no longer executed

Logical non-:!

1. You can use logical symbols after a condition test to determine whether the second instruction executes

2. Determine the logical relationship between commands by using the control structure of the conditional judgment

   eg:[expression] && statement1 | | Statement2

   Indicates that if the test expression is true, statement 1 is executed, or statement 2 is executed

   
   

   
   

If control structure:

if judgment condition; then

Statement

Fi

if judgment condition; then

Statement1

Else

Statement2

Fi

Note: The return value type of the judging condition must be Boolean type

file test: -e/path/to/filename test file is present

-F test Specifies that the file is not a normal file

-D test Specifies whether the file is a directory file

-R tests whether the file has Read permissions

-W Tests if the file has write permissions

-X tests whether the file has Execute permissions

String Test: =

==

Equal and double equals, [string1 = string2] Tests whether two strings are equal

-N String tests whether the specified string is empty and Null is true

-S string tests whether the specified string is not empty and is not empty for true

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Conditional test in Shell