Chmod Command for Beginners

There are two way to give file/directory permissions using bits and symbolic representation . In this article, let us discuss how to use symbolic representation with chmod.

we are having 3 different roles of symbolic representation user, group and others.The representation given below:

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

we also have 3 symbolic representation of file/directory permissions. they are :

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

And we also have +, – and = symbols :

  • + means Add,
  • – means Remove,
  • = means set the permissions exactly like this.

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

1.Add a permission to file/directory

chmod g+w filename

Changing permission to a single set. + symbol means adding permission. Here we are giving group to write permission. Likewise you can give single permission(r/w/x) for any roles(u/g/o).

2. Remove permission from a file/directory

$ chmod u-x filename

This will remove execute permission from user.

3. Add multiple permission to a file/directory

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

$ chmod u+r,g+x filename

4.Remove multiple permission from a file/directory

$ chmod u-rx filename

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

$ chmod a+x filename

It will change the permission of all three roles such as user,group and others.

6. Set a permission of a file/directory

$ chmod u=w filename

7.Set multiple permission of a file/directory

$ chmod u=rwx filename

It will set the permission. This will replace the permission with given permission.

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