If judgment in Shell

Tag: String null

Integer comparison:

-EQ equals to, for example, if ["$ A"-EQ "$ B"]

-Ne is not equal to, for example, if ["$ A"-ne "$ B"]

-GT is greater than, for example, if ["$ A"-GT "$ B"]

-Ge is greater than or equal to, for example, if ["$ A"-ge "$ B"]

-Lt is less than, for example, if ["$ A"-lt "$ B"]

-Le is less than or equal to, for example, if ["$ A"-Le "$ B"]

<Less than (double parentheses are required), such as: ("$ A" <"$ B "))

<= Less than or equal to (double parentheses are required), for example: ("$ A" <= "$ B "))

> Greater than (double parentheses are required), such as: ("$ A"> "$ B "))

> = Equal to or greater than (double parentheses required), for example: ("$ A"> = "$ B "))

String comparison:

= Equals, for example, if ["$ A" = "$ B"]

= Equal to, such as: If ["$ A" = "$ B"]

! = Reverse, for example, if ["$ "! = "$ B"]

-Z string is "null". The length is 0.
-N string is not "null"

Other judgment parameters:

-E file exists
-File A exists (discarded)
-F determines that the file is a regular file (normal file, non-directory or device)
-S file length is not 0
-D: determines that the object is a directory.
-B determines that the object is a block device.
-C: determines that the object is a character device.
-P: the object to be determined is a pipeline.
-H indicates that the file is a symbolic connection.
-L identify the file as a symbolic connection
-S (uppercase) determines that the file is a socket
-T is the file descriptor associated with a terminal device. The stdin [-T0] or [-T1] used to detect scripts is a terminal.
-The R file has read permission for the user who runs the script
-W file has write permission for the user who runs the script
-The X file has the execution permission for the user who runs the script.
-U set-user-ID (SUID) indicates the file, that is, the root permission file that common users can use, implemented through chmod + S File
-K: Set the pasting position
-O the user who runs the script is the file owner.
The Group-ID of the-G file is the same as the user who runs the script.
-N: indicates whether the object has been modified since it was last read.

F1-nt F2 file F1 is newer than F2
Is F1-ot F2 earlier than F2?
Does F1-Ef F2 file F1 and F2 hard connect to the same file?

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If judgment in Shell