When executed, the command can change file system modes of files and directories. The modes include permissions and special modes.
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2 Sample use 3 Usage 4 External links |
chmod +rw file.txt
The chmod command will change the permissions of the file file.txt to read and write for all.
chmod -R u+w go-w docs/
The chmod command will change the permissions of the directory docs and all its contents to add write access for the user, and deny write access for everybody else.
chmod switches modes files
There are permissions and special modes. The permissions are:
r - read permission;
For each file is specified which permissions apply to the owner of the file, users in the group of the file, or all other users.
The modes can be specified in two ways, with characters or octal numbers. For characters, there are modification operators such that + adds the mode, = sets the mode, and - removes the mode setting.
Specified as:
In octal mode, four numbers are specified and used to set the mode of a file. For owner, group and other the value of each setting is added and the modes are concatenated. The modes are given the values r 4;
w 2; x 1.
Specified as:History
A chmod command appeared in AT&T UNIX version 1.
Sample use
Example:Usage
The chmod command options are specified like this:Switches
chmod has a number of command line options, or "switches", that can modify the output. Some of these options are
-R: recursively modify modes of all files in subdirectories.
-h: if the file specified is a soft link, change the mode of the link itself rather than the file that the link points to.
-v: verbose. List all files as they are being processedModes
w - write permission;
x - execute permission;
+r read is added for all;
u=rw go= read and write is set for the owner, all permissions are cleared for the group and others;
-x execute permission is removed for all;
0755 - Equivalent to u=rwx go=rx. The 0 specifies no special modes.