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This page displays the COHERENT manpage for paths [Routing data base for mail].
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paths -- System Administration Routing data base for mail /usr/lib/mail/paths File /usr/lib/mail/paths holds the data base that the command smail uses to route mail. Each line gives routing information to a host, and has the following format: host route [cost] host names a remote host. The route field details the route by which mail can travel from your system to host. Note that it includes the printf()- style format string ``%s''. This field uses the bang-path format for describing a route. For example, if you access site foo via site bar, then route field for site bar reads: bar foo!bar!%s smail uses the optional field cost to decide whether to queue mail that is spooled for other systems, or to invoke the command uucico to deliver the mail immediately. If the cost is at or below smail's ``queueing threshold'', then smail attempts to deliver it immediately. This speeds mail delivery between hosts that enjoy an inexpensive UUCP link, such as a serial line; and batches mail that must be sent over expensive media, such as long-distance telephone. If the cost field is absent, smail gives this host a cost value above that of its queueing threshold. Note that the value in the costs field does not override the connection times set in the UUCP file sys. Thus, this field is useful only for systems that you can call any time, or that you call frequently. Example The following gives a sample paths file for a COHERENT system named lepanto: friend friend!%s 300 hubsys hubsys!%s 95 lepanto %s 0 lepanto.ampr.org %s0 widget hubsys!widget!%s95 As this file shows, lepanto is linked to systems hubsys and friend. The cost of 95 associated with hubsys is low, and is appropriate to a low-cost link, such as a hard-wired link. On the other hand, the cost of 300 associated with friend is high, which indicates that the connection with friend is expensive, such as a long-distance telephone connection. If cost is 100 or greater, mail will be queued for later delivery. A cost below 100 tells smail to attempt immediate delivery. In this example, machine lepanto is registered in the domain ampr.org. ``ampr'' is an abbreviation for ``Amateur Packet Radio,'' which indicates that lepanto is a packet-radio node. Note that machine name lepanto appears in both conventional form (``lepanto'') and domain form (``lepanto.ampr.org''); this is done to make it easier for smail to resolve addresses. lepanto can use hubsys to forward mail to widget. Thus, when smail receives mail for system widget, it will transmit it to hubsys for forwarding. Note that hubsys's administrator must have given lepanto permission to use it as a mail relay, or this will not work. See Also Administering COHERENT, mail [overview], smail Notes Please note that the mail-routing program smail does not actually read /usr/lib/mail/paths when it processes mail; rather, it reads a DBM-style data base that is built from this file. The DBM data base can be read much faster than an ordinary text file, thus improving the speed with which smail handles mail. Thus, when you edit paths, you must invoke the command mkpaths to ``cook'' its contents into DBM format, so smail see the changes you have made. For information on DBM-style data bases, see the Lexicon entry for libgdbm.