chmod :: Knowledge Base (KB)

chmod

Unix

Chmod

Usage

chmod [OPTION]... MODE[,MODE]... FILE...

Flags

Usage: chmod [OPTION]... MODE[,MODE]... FILE...
  or:  chmod [OPTION]... OCTAL-MODE FILE...
  or:  chmod [OPTION]... --reference=RFILE FILE...
Change the mode of each FILE to MODE.
With --reference, change the mode of each FILE to that of RFILE.

  -c, --changes          like verbose but report only when a change is made
  -f, --silent, --quiet  suppress most error messages
  -v, --verbose          output a diagnostic for every file processed
      --no-preserve-root  do not treat '/' specially (the default)
      --preserve-root    fail to operate recursively on '/'
      --reference=RFILE  use RFILEs mode instead of MODE values
  -R, --recursive        change files and directories recursively
      --help     display this help and exit
      --version  output version information and exit

Each MODE is of the form '[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'.

GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
Full documentation at: <https://www.gnu.org/software/coreutils/chmod>
or available locally via: info '(coreutils) chmod invocation'

Chmod Rights

r - Read rights
w - Write rights
x - Execute rights

Number	Permissions	Build-up
0	- - -	0+0+0
1	- - x	0+0+1
2	- w -	0+2+0
3	- w x	0+2+1
4	r - -	4+0+0
5	r - x	4+0+1
6	r w -	4+2+0
7	r w x	4+2+1

Example privilege string rwxr--r--

First block is rights for the specific user
Second block is rights for the specific group
Third block is rights for everyone else

Examples

Change permissions of ’testfile.txt'

$ ll testfile.txt
-rwxrwxrwx 1 b b 72 mrt  9 20:53 testfile.txt

$ chmod 400 testfile.txt

$ ll testfile.txt
-r-------- 1 b b 72 mrt  9 20:53 testfile.txt

Add execution permissions

$ ll testfile.txt
-r-------- 1 b b 72 mrt  9 20:53 testfile.txt

$ chmod +x testfile.txt

$ ll testfile.txt
-r-x--x--x 1 b b 72 mrt  9 20:53 testfile.txt

Add execution permissions for only the user

$ ll testfile.txt
-r-------- 1 b b 72 mrt  9 20:53 testfile.txt

$ chmod u+x testfile.txt

$ ll testfile.txt
-r-x------ 1 b b 72 mrt  9 20:53 testfile.txt

URL List

GNU.org