DOKK / manpages / debian 10 / bcron / bcrontab.1.en
bcrontab(1) General Commands Manual bcrontab(1)

bcrontab - Manage users crontab files

bcrontab [ -u user ] file

bcrontab [ -u user ] { -l | -r | -e }

bcrontab interfaces with the bcron-spool daemon to manage crontab files in the privileged spool directory.

Tell bcron-spool that we are acting on behalf of the named user. bcron-spool will only accept the username if bcrontab is running as either root or the same user ID as the named user.
List the cronab crontab to standard output.
Remove the user's crontab.
Edit the current crontab.

If this is set, it is used as the editor to invoke to edit a crontab.
If $VISUAL is not set and this is, it is used as the editor to invoke to edit a crontab. If neither are set, /bin/vi is used.
The path to the named socket used to communicate with bcron-spool. Defaults to /var/run/bcron-spool.
These two variables are used, in order, to determine the user name invoking the program. One must be set if the -u option is not used.

bcrontab tries to writes a temporary file into the current directory, and then into /tmp if that fails, in order to edit the current crontab.

bcron-spool(8), crontab(5)

Bruce Guenter <bruce@untroubled.org>