newgrp

The "newgrp" command line tool is used to change the primary group of a user in Unix-like operating systems. When a user creates a new file or directory, it is assigned the user's primary group by default. However, the "newgrp" command allows the user to switch to a different primary group temporarily.

To use the "newgrp" command, the user must provide it with the name of the group they wish to switch to. If the user is a member of the specified group, a new shell is created with the changed primary group. This new shell inherits all the environment variables and privileges of the original shell.

The "newgrp" command requires the user to enter their password, except for when they are switching to a group they are already a member of or when they have the necessary permissions to execute the command without entering a password. This extra security measure ensures that only authorized users can change their primary group.

The "newgrp" command is particularly useful in environments where different groups may have varying access levels to files and directories. It allows users to work collaboratively with members of different groups without permanently changing their primary group.

Once the user exits the new shell, they are returned to their original primary group in the original shell. The "newgrp" command does not affect the user's secondary groups, only the primary group is changed temporarily.