Bash Shell Foundation II conditional judgment

if condition judgment; Then

Statment

Else

Statment

Fi

Or

if condition judgment; Then

Statment

Elif

Statment

Fi

Anti-quote: Returns the execution result of the command to the variable.

Set UserID

UserID = ' Id-u user1 '

command to end a script prematurely: exit: Exits the current process. is to exit the script

The end of any program has an execution status result and execution result. If get is the state result of the command

Exit to define the execution status results of the script.

Exit 0~255,0 is correct, 1~255 is error.

！ Represent non, take counter action

if! grep ' ^work\> '/etc/passwd &>/dev/null; Then

echo "User does not exist"

Fi

Integer test:

-GT: Greater Than

-eq: Equals

-LT: Less than

-ne: Not equal to

-ge: greater than or equal to

-le: Less than or equal to

File test:

-E: Whether the file exists

-F: Test whether the file is a normal file

-D: Tests whether the specified path is a directory

-R: Tests whether the specified file is readable to the current user

-W: Tests whether the specified file is writable for the current user

-X: Tests whether the specified file is executable for the current user

This article is from the Linux learning blog, so be sure to keep this source http://884482.blog.51cto.com/874482/1697174

Bash Shell Foundation II conditional judgment