man vipw (Administration système) - edit the password, group, shadow-password or shadow-group file.
NAME
vipw, vigr - edit the password, group, shadow-password or shadow-group file.
SYNOPSIS
vipw [-s]
vigr [-s]
DESCRIPTION
vipw and vigr will edit the files /etc/passwd and /etc/group, respectively. With the -s flag, they will edit the shadow versions of those files, /etc/shadow and /etc/gshadow, respectively. The programs will set the appropriate locks to prevent file corruption. When looking for an editor, the programs will first try the environment variable $VISUAL, then the environment variable $EDITOR, and finally the default editor, vi(1).