comsat(8)

comsat8

Biff server

Usage

comsat

Overview

The comsat utility is the server process which receives reports of incoming mail and notifies users if they have requested this service. The comsat utility receives messages on a datagram port associated with the “biff” service specification (see services(5) and inetd(8)). The one line messages are of the form:

user@mailbox-offset[:mailbox-name]

If the user specified is logged in to the system and the associated terminal has the owner execute bit turned on (by a “biff y”), the offset is used as a seek offset into the appropriate mailbox file and the first 7 lines or 560 characters of the message are printed on the user's terminal. Lines which appear to be part of the message header other than the “From”, “To”, “Date”, or “Subject” lines are not included in the displayed message.

If the user specified is logged in to the system and the associated terminal has the group execute bit turned on (by a “biff b”), two bell characters (ASCII \007) are printed on the user's terminal.

If mailbox-name omitted, standard mailbox assumed.

Files

/var/run/utx.active

to find out who is logged on and on what terminals

/var/mail/user

standard mailbox

Releases

87 releases since FreeBSD 2.0.5-RELEASE; the text changed 43 times.

  1. 2.0.5–2.1.7.1
  2. 2.2.2–2.2.8
  3. 2.2.9
  4. 3.0–3.2
  5. 3.3–3.5.1
  6. 4.0–4.2
  7. 4.3
  8. 4.4–4.6.2
  9. 4.7–4.11
  10. 5.0–5.5
  11. 6.0–6.3
  12. 6.4
  13. 7.0
  14. 7.1
  15. 7.2
  16. 7.3
  17. 7.4
  18. 8.0
  19. 8.1
  20. 8.2
  21. 8.3
  22. 8.4
  23. 9.0
  24. 9.1
  25. 9.2
  26. 9.3
  27. 10.0
  28. 10.1
  29. 10.2
  30. 10.3
  31. 10.4
  32. 11.0
  33. 11.1
  34. 11.2
  35. 11.3
  36. 11.4
  37. 12.0
  38. 12.1
  39. 12.2
  40. 12.3
  41. 12.4
  42. 13.0–13.2
  43. 13.3–14.5
  44. 15.0–16.0

History

The comsat utility appeared in 4.2BSD.

Bugs

The message header filtering is prone to error. The density of the information presented is near the theoretical minimum.

Users should be notified of mail which arrives on other machines than the one to which they are currently logged in.

The notification should appear in a separate window so it does not mess up the screen.

From base 16.0-CURRENT-20261027-61c70dc16a79 in FreeBSD 16.0-CURRENT (2026-10-27). Parsed by carta from the page's mdoc source.