Linux-shell Test

The nature of the test:

is an action command

Determine if the condition is true based on the $? return value

Operating Specifications:

Format 1:test conditional expression

Format 2: [Conditional expression]

Contact method for the test operation:

Direct root && echo YES to determine results

Usage: [conditional expression] && echo YES

Test examples:

[-D "/etc/fstab"] && echo YES

[-D "/boot/fstab"] && echo YES

[-F "/etc/fstab"] && echo YES

[-F "/boot"] && echo YES

Presence and Identification:

-E: Whether the target exists

-D: Whether it is a directory

-F: Whether it is a file

Detection of permissions:

-r: Read permission

-W Write permission

-X whether there are executable (excute) permissions

Integer value comparison:

-eq Equals (equal)

-ne not equal to (not equal)

-GT greater than (greater than)

-lt less than (lesser than)

-ge greater than or equal to (greater or equal)

-le less than or equal to (lesser or equal)

Integer value comparison:

[$ (who | wc-l)-eq 2] && echo YES

[$USER = "root"] && echo YES

Linux-shell Test