7 Chmod Command Examples for Beginners

In this article, let us review how to use symbolic representation with chmod.

Following are the symbolic representation of three different roles:

  • u is for user,
  • g is for group,
  • and o is for others.

Following are the symbolic representation of three different permissions:

  • r is for read permission,
  • w is for write permission,
  • x is for execute permission.

Following are few examples on how to use the symbolic representation on chmod.

1. Add single permission to a file/directory




Changing permission to a single set. + symbol means adding permission. For example, do the following to give execute permission for the user irrespective of anything else:

$ chmod u+x filename

2. Add multiple permission to a file/directory

Use comma to separate the multiple permission sets as shown below.

$ chmod u+r,g+x filename

3. Remove permission from a file/directory

Following example removes read and write permission for the user.

$ chmod u-rx filename

4. Change permission for all roles on a file/directory

Following example assigns execute privilege to user, group and others (basically anybody can execute this file).

 

 

$ chmod a+x filename

5. Make permission for a file same as another file (using reference)




If you want to change a file permission same as another file, use the reference option as shown below. In this example, file2’s permission will be set exactly same as file1’s permission.

$ chmod --reference=file1 file2

6. Apply the permission to all the files under a directory recursively

Use option -R to change the permission recursively as shown below.

$ chmod -R 755 directory-name/

7. Change execute permission only on the directories (files are not affected)

On a particular directory if you have multiple sub-directories and files, the following command will assign execute permission only to all the sub-directories in the current directory (not the files in the current directory).

$ chmod u+X *

Note: If the files has execute permission already for either the group or others, the above command will assign the execute permission to the user

Source http://www.thegeekstuff.com