The comsat server receives reports of incoming mail and notifies users who request this service. comsat is invoked by the inetd(8) daemon when it receives messages on a datagram port associated with the biff(1) service specification in /etc/services(4). The datagram contains a 1-line message of the form: user@mailbox-offset If the user specified is logged in and the associated terminal has the owner execute bit turned on (with biff y), offset is used as a seek offset into the file named in mailbox. The first 7 lines or 560 characters of the message are printed on the user's system. The message excludes mail header lines other than the From or Subject lines.
The comsat command always tries to convert incoming mail messages from the mail interchange codeset to the user's application codeset. It determines the mail interchange code first by checking the mail message itself to see if it contains the required information. Otherwise, the system-wide default mail interchange code in the file /usr/lib/mail-codesets will be used. If no such system file exists, no codeset conversion will be performed.
The determination of the user's application code in each terminal session is by one of the following methods. The application codeset defined in the user's Asian tty driver. The codeset name stored in the ~/.codesetdevname file, where devname is the name of the terminal device for the current terminal session. You can obtain the value of devname by issuing the tty command. For example, if the tty command returns /dev/ttys8, use ttys8 as the value for devname. The lang valued option defined in $HOME/.mailrc or /usr/share/lib/Mail.rc.
Commands: biff(1), inetd(8), mailx(1), mh(1)
Files: services(4), inetd.conf(4), tty(7) delim off