|-l||Simulate a full login. The environment and umask are set to what would be expected if the user actually logged in again.|
If the group operand is present, a new shell is started with the specified effective and real group IDs. The user will be prompted for a password if they are not a member of the specified group.
Otherwise, the real, effective and supplementary group IDs are restored to those from the current users password database entry.
The newgrp utility attempts to start the shell regardless of whether group IDs were successfully changed.
If an error occurs and the shell cannot be started, newgrp exits >0. Otherwise, the exit status of newgrp is the exit status of the shell.
The newgrp utility conforms to -p1003.1-2001.
A newgrp utility appeared in AT&T v6 .
For security reasons, the newgrp utility is normally installed without the setuid bit. To enable it, run the following command:chmod u+s /usr/bin/newgrp
Group passwords are inherently insecure as there is no way to stop users obtaining the password hash from the group database. Their use is discouraged. Instead, users should simply be added to the necessary groups.