edit the password or group file
vipw edits the password file after setting the appropriate locks, and does any necessary processing after the password file is unlocked. If the password file is already locked for editing by another user, vipw will ask you to try again later. The default editor for vipw and vigr is vi(1). vigr edits the group file in the same manner as vipw does the passwd file.
If the following environment variable exists, it will be utilized by vipw and vigr:
The editor specified by the string EDITOR will be invoked instead of the default editor vi(1).
The vipw command appeared in 4.0BSD.
The vigr command appeared in Util-Linux 2.6.
The vigr and vipw commands are part of the util-linux package and are available from Linux Kernel Archive.