chmod (Change Mode): A Linux command to change the permissions of a file or directory. See man chmod. See file ownership and permissions in Linux.

The following quotes are extracted from emails by Paul F. Ryan and Anita Lewis on the blt mailing list:

Paul wrote:
chmod has the symbolic '=' operator, which alows setting permission without knowing the current state of the permission.  For instance:   * chmod u=rwx,g=rx,o= somefile*  is equivalent to the command:   * chmod 750 somefile* Both will set the permissions regardless of the previous state of the permission bits.

Thanks Paul, I looked at man chmod It states: The operator '+' causes the permissions selected to be added to the existing permissions of each file; '-' causes them to be removed; and '=' causes them to be the only permissions that the file has.

So if for example the permissions for group were already rw and you ran chmod g+rx you would end up with rwx.  But if you ran chmod g=rx you would end up with just rx.  

Contributors

• RandyKramer - 15 Jan 2002
• GrantFraser - quoted portions of emails by Paul F. Ryan and Anita Lewis on the blt mail list - 18 Jan 2002
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