The vipw utility 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 is vi(1).
When run without options, vipw will work with the password files in /etc. The -d option may be used to specify an alternative directory to work with.
The vipw utility performs a number of consistency checks on the password entries, and will not allow a password file with a "mangled" entry to be installed. If vipw rejects the new password file, the user is prompted to re-enter the edit session.
Once the information has been verified, vipw uses pwd_mkdb(8) to update the user database. This is run in the background, and, at very large sites could take several minutes. Until this update is completed, the password file is unavailable for other updates and the new information is not available to programs.
If the following environment variable exists it will be utilized by vipw: