example:
# pw usermod -n username -g groupname
PW(8) FreeBSD System Manager's Manual PW(8)
NAME
pw -- create, remove, modify & display system users and groups
SYNOPSIS
pw [-V etcdir] useradd [nameuid] [-C config] [-q] [-n name] [-u uid]
[-c comment] [-d dir] [-e date] [-p date] [-g group] [-G grouplist]
[-m] [-M mode] [-k dir] [-w method] [-s shell] [-o] [-L class]
[-h fd -H fd] [-N] [-P] [-Y]
pw [-V etcdir] useradd [nameuid] -D [-C config] [-q] [-b dir] [-e days]
[-p days] [-g group] [-G grouplist] [-k dir] [-M mode] [-u min,max]
[-i min,max] [-w method] [-s shell] [-y path]
pw [-V etcdir] userdel [nameuid] [-n name] [-u uid] [-r] [-Y]
pw [-V etcdir] usermod [nameuid] [-C config] [-q] [-n name] [-u uid]
[-c comment] [-d dir] [-e date] [-p date] [-g group] [-G grouplist]
[-l name] [-m] [-M mode] [-k dir] [-w method] [-s shell] [-L class]
[-h fd -H fd] [-N] [-P] [-Y]
pw [-V etcdir] usershow [nameuid] [-n name] [-u uid] [-F] [-P] [-7] [-a]
pw [-V etcdir] usernext [-C config] [-q]
pw [-V etcdir] groupadd [groupgid] [-C config] [-q] [-n group] [-g gid]
[-M members] [-o] [-h fd -H fd] [-N] [-P] [-Y]
pw [-V etcdir] groupdel [groupgid] [-n name] [-g gid] [-Y]
pw [-V etcdir] groupmod [groupgid] [-C config] [-q] [-n name] [-g gid]
[-l name] [-M members] [-m newmembers] [-d oldmembers] [-h fd -H fd]
[-N] [-P] [-Y]
pw [-V etcdir] groupshow [groupgid] [-n name] [-g gid] [-F] [-P] [-a]
pw [-V etcdir] groupnext [-C config] [-q]
pw [-V etcdir] lock [nameuid] [-C config] [-q]
pw [-V etcdir] unlock [nameuid] [-C config] [-q]
