chmod stands for "change mode". It is used to change the permissions to files/ directories

Syntax

chmod [options] <permissions> <file_name> 

Options

Option	Description
-R	change permissions for files and directories recursively
-v	Verbose(this display all the files that the command is processing)
-c	Change (this will display only the files it is changing the permission for)
-f	silent mode (this will supress errors)
-h	this change the permission of the symbolic link instead of the main file

Example

chmod 777 foo.txt

Permissions

Following are the four possible digits and their respective permissions

Digit	Permission
4	read
2	write
1	execute
0	no permission

Users can also sumup these digits and can use like following

Derived Digits	Permission
7	4+2+1 = read + write + execute
6	4+2 = read + write
5	4+1 = read + execute
3	2+1 = write + execute

Permissions for user, group, others

Owner of the file can set different permissions for user, group & others

Example

chmod u=rwx,g=rx,o=r foo.sh # this is same as chmod 754 foo.sh

u = user
g = group
o = others

r = read
w = write
x = execute