Bash shell condition test

3 Kinds of TEST commands:

Test EXPRESSION

[EXPRESSION]

[[EXPRESSION]]

Note: You must have a white space character before and after expression

Test type of Bash

Numerical test:

-eq: Is it equal

-ne: Whether or not to wait

-ge: is greater than or equal to

-le: is less than or equal to

-GT: Is it greater than

-LT: Is it less than

String test:

= or = =: is equal to

: Is it greater than

<: is less than

! =: is not equal to

=~: Whether the left string can be used in the right pattern matching [[]]

-Z "string": test whether the string is empty and Null is true

-N "string": test whether the string is non-empty, not empty is true

Note: The operands used for string comparisons should be enclosed in quotation marks.

File test:

Existence test:

-a FILE: Same as Next

-e File: Test for existence of files, existence is true, otherwise false

Presence and category testing:

-B File: Exists and is a block device file

-C file: exists and is a character device file

-D file: Exists and is a catalog file

-F file: exists and is a normal file

-H file or-L file: exists and is a symbolic link file

-P file: exists and is a named pipe file

-S file: exists and is a socket file

File permission test:

-R FILE: exists and is readable

-W FILE: exists and is writable

-X FILE: exists and is executable

File Special Permissions Test:

-G FILE: Exists and has Sgid permissions

-U FILE: Exists and has suid permissions

-K FILE: Exists and has sticky permissions

File size test:

-S FILE: exists and is not empty

Whether the file is open:

-T FD:FD indicates whether the file descriptor is open and related to a terminal

Other:

-N File: Whether the file has been modified since the last time it was read

-O File: Whether the current active user is a file owner

-G file: whether the current active user is a group of files

Binocular test:

File1-ef whether File2:file1 and FILE2 point to the same inode on the same device

File1-nt File2:file1 is new to FILE2

File1-ot file2:file1 whether old and FILE2

Combination condition test:

Logical operation:

Used in []:

Expression1-a expression2:2 conditions are true at the same time, the result is true

Expression1-o Expression2:2 One of the conditions is true, the result is true

! Expression: The result is true when the condition is false

[[]] or [] * * [] Use: NOTE: * * for && or | |

&&: Both the left and right conditions or commands are true at the same time, the result is true

|| : The result is true when one of the conditions or commands on either side is true

!: The result is true when the condition or command is False

Note: The use of parentheses in [] requires escaping that is \ (\), [[]] without escaping

　　　　　

　　　　　　　　　　

　　　　　　　　　　

　　　　　　

　　　　　　

Bash shell condition test