chmod
Change access permissions, change mode.
Usage: chmod [Options]... MODE [,MODE]... File...
chmod [Options]... NUMERIC_MODE File...
chmod [Options]... --reference=RFILE File...
options:
-f, --silent, --quiet suppress most error messages
-v, --verbose output a diagnostic for every file processed
-c, --changes like verbose but report only when a change is made
--reference=RFILE use RFILE's mode instead of MODE values
-R, --recursive change files and directories recursively
--help display help and exit
--version output version information and exit
chmod changes the permissions of each given file according to MODE, which can be either an octal number representing the bit pattern for the new permissions or a symbolic representation of changes to make, (+-= rwxXstugoa)
Numeric mode:
From one to four octal digits
Any omitted digits are assumed to be leading zeros.
The first digit = selects attributes for the set user ID (4) and set group ID (2) and save text image (1)S
The second digit = permissions for the user who owns the file: read (4), write (2), and execute (1)
The third digit = permissions for other users in the file’s group: read (4), write (2), and execute (1)
The fourth digit = permissions for other users NOT in the file’s group: read (4), write (2), and execute (1)
The octal (0-7) value is calculated by adding up the values for each digit
User (rwx) = 4+2+1 = 7
Group(rx) = 4+1 = 5
World (rx) = 4+1 = 5
chmode mode = 0755
Examples
chmod 400 file - Read by owner
chmod 040 file - Read by group
chmod 004 file - Read by world
chmod 200 file - Write by owner
chmod 020 file - Write by group
chmod 002 file - Write by world
chmod 100 file - execute by owner
chmod 010 file - execute by group
chmod 001 file - execute by world
To combine these just add the numbers together:
chmod 444 file - Allow read permission to owner and group and world
chmod 777 file - Allow everyone to read, write, and execute file
