The newgrp command logs a user into a new group by changing a user's real and effective group ID. The user remains logged in and the current directory is unchanged. The execution of newgrp always replaces the current shell with a new shell, even if the command terminates with an error (unknown group).

Any variable that is not exported is reset to null or its default value. Exported variables retain their values. System variables (such as PS1, PS2, PATH, MAIL, and HOME), are reset to default values unless they have been exported by the system or the user. For example, when a user has a primary prompt string (PS1) other than $ (default) and has not exported PS1, the user's PS1 will be set to the default prompt string $, even if newgrp terminates with an error. Note that the shell command export (see sh(1) and set(1)) is the method to export variables so that they retain their assigned value when invoking new shells.

With no operands and options, newgrp changes the user's group IDs (real and effective) back to the group specified in the user's password file entry. This is a way to exit the effect of an earlier newgrp command.

A password is demanded if the group has a password and the user is not listed in /etc/group as being a member of that group. The only way to create a password for a group is to use passwd(1), then cut and paste the password from /etc/shadow to /etc/group. Group passwords are antiquated and not often used.

Equivalent to exec newgrp argument where argument represents the options and/or operand of the newgrp command.

Equivalent to exec to/bin/newgrp argument where argument represents the options and/or operand of the newgrp command.

On this man page, ksh(1) commands that are preceded by one or two * (asterisks) are treated specially in the following ways:

1. Variable assignment lists preceding the command remain in effect when the command completes.
2. I/O redirections are processed after variable assignments.
3. Errors cause a script that contains them to abort.
4. Words, following a command preceded by ** that are in the format of a variable assignment, are expanded with the same rules as a variable assignment. This means that tilde substitution is performed after the = sign and word splitting and file name generation are not performed.