32v 1m newgrp
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NEWGRP(1) UNIX Programmer's Manual NEWGRP(1)
newgrp - log in to a new group
_N_e_w_g_r_p changes the group identification of its caller, analogously to _l_o_g_i_n(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.
A password is demanded if the group has a password and the user himself does not.
When most users log in, they are members of the group named `other.' _N_e_w_g_r_p is known to the shell, which executes it directly without a fork.