Shell test, shelltest

Shell test, shelltest

Test command usage. Function: Checks files and comparison values.

1) judgment Expression

If test (expression true)

If test! The expression is false.

Test expression 1-a expression 2 both are true

Test expression 1-o expression 2 one of the two expressions is true

2) judge the string

The length of the test-n string is non-zero.

The length of the test-z string is zero.

Test string 1 = string 2 strings are equal

Test string 1! = String 2 string

3) judge the integer

Test integer 1-eq integer 2 integer equal

Test integer 1-ge integer 2 integer 1 is greater than or equal to integer 2

Test integer 1-gt integer 2 integer 1 is greater than integer 2

Test integer 1-le integer 2 integer 1 less than or equal to integer 2

Test integer 1-lt integer 2 integer 1 less than integer 2

Test integer 1-ne integer 2 integer 1 is not equal to integer 2

4) file judgment

Test File1-ef File2 two files have the same device number and I node number

Test File1-nt File2 file 1 is newer than file 2

Test File1-ot File2 file 1 is older than file 2

The test-B File exists and is a block device File.

The test-c File exists and is a character device File.

The test-d File exists and is a directory.

The test-e File exists.

The test-f File exists and is a regular File.

The test-g File exists and the group ID is set.

The test-G File exists and belongs to the valid group ID.

The test-h File exists and is a symbolic link (same as-L)

The test-k File exists and the sticky bit is set.

The test-B File exists and is a block device File.

The test-L File exists and is a symbolic link (same as-h)

The test-o File exists and is a valid user ID.

The test-p File exists and is a named pipe.

The test-r File exists and is readable.

The test-s File exists and is a socket.

The test-t FD file descriptor is opened on a terminal.

The test-u File exists and its set-user-id bit is set.

The test-w File exists and can be written.

The test-x File exists and can be executed.

Who can explain a shell command, if test! -H // Home

This is a judgment expression.
Use man test to view the help of the test command:
-H FILE
FILE exists and is a symbolic link (same as-L)
The file exists and is a character Link (the same as the-L option ).

! EXPRESSION
EXPRESSION is false
The expression is false, that is, "Non" Operation ("reverse" operation ).

Therefore, the meaning of this judgment statement is:
If the file ../Home does not exist, or the file exists but is not a character link.

If it is a character link, use ls-l.../../Home to see a link symbol-> link to another file. For example:
$ Ls-l/bin/sh
Lrwxrwxrwx 1 root 4 Mar 16 2009/bin/sh-> bash

Shell programming if, test command, where is my understanding wrong?

If test-z $1
Then echo 'Please input a file name'; exit # Add an exit ticket
Else
...
Otherwise, if test-x $1 will return an error