newgrp command Tips Linux Tips by Donald Burleson

Logging on to another Group with newgrp

Every Linux user can be assigned to multiple groups so they can obtain access to whatever files and directories they need to perform their work.  Users can determine the groups to which they have access by using the id command. 

When a user logs on to the system, however, they are assigned to their primary group as specified by the Systems Administrator when the user ID was created.  Since Linux only allows a user to be logged into one group at a time, there is a command that allows users to change their current group whenever they need to assume the permissions of another group.

The newgrp command allows users to change their current group to any group they have been added to.  The newgrp command accepts a single parameter consisting of the group name into which the user wished to log.

The following example shows the use of the id command to determine the group into which the user is already logged in to as well as all of the groups to which that user has been granted access.  In the example, the current user id (uid) is tclark and the current group (gid) is also tclark.  The eligible groups are tclark and authors.

Determining a User's Current Group and Accessible Groups Using the id Command

$ id
uid=503(tclark) gid=504(tclark) groups=504(tclark),506(authors)

The next example shows how to switch from the current group of tclark to the authors group.

Logging into a Different Group Using the newgrp Command

$ id
uid=503(tclark) gid=504(tclark) groups=504(tclark),506(authors)
$ newgrp authors
$ id
uid=503(tclark) gid=506(authors) groups=504(tclark),506(authors)

 

This is an excerpt from "Easy Linux Commands" by Linux guru Jon Emmons.  You can purchase it for only $19.95 (30%-off) at this link.