Provided by: login_4.16.0-2+really2.40.2-14ubuntu1_amd64 

NAME
newgrp - log in to a new group
SYNOPSIS
newgrp [group [command]] newgrp [-c command] [group]
DESCRIPTION
newgrp changes the group identification of its caller, analogously to login(1). The same person remains logged in, and the current directory is unchanged, but calculations of access permissions to files are performed with respect to the new group ID. If no group is specified, the GID is changed to the login GID. An optional command can be specified, which is invoked after group change instead of the user’s shell.
OPTIONS
-c, --command=command Pass command to the user’s shell with the -c option. -h, --help Display help text and exit. -V, --version Print version and exit.
FILES
/etc/group, /etc/passwd
AUTHORS
Originally by Michael Haardt. Currently maintained by Peter Orbaek <poe@daimi.aau.dk>.
SEE ALSO
login(1), group(5)
REPORTING BUGS
For bug reports, use the issue tracker at https://github.com/util-linux/util-linux/issues.
AVAILABILITY
The newgrp command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>.