By default uucp and uux will automatically start up
uucico to call another system whenever work is queued up.
However, the call may fail, or you may have put in time restrictions
which prevent the call at that time (perhaps because telephone rates are
high) (see section When to Call). Also, a remote system may have work
queued up for your system, but may not be calling you for some reason
(perhaps you have agreed that your system should always place the call).
To make sure that work gets transferred between the systems withing a
reasonable time period, you should arrange to periodically invoke
uucico.
These periodic invocations are normally triggered by entries in the `crontab' file. The exact format of `crontab' files, and how new entries are added, varies from system to system; check your local documentation (try `man cron').
To attempt to call all systems with outstanding work, use the command `uucico -r1'. To attempt to call a particular system, use the command `uucico -s system'. To attempt to call a particular system, but only if there is work for it, use the command `uucico -C -s system'. (see section Invoking uucico).
A common case is to want to try to call a system at a certain time, with periodic retries if the call fails. A simple way to do this is to create an empty UUCP command file, known as a poll file. If a poll file exists for a system, then `uucico -r1' will place a call to it. If the call succeeds, the poll file will be deleted.
A poll file can be easily created using the `uux' command, by requesting the execution of an empty command. To create a poll file for system, just do something like this:
uux -r system!
The `-r' tells `uux' to not start up `uucico' immediately. Of course, if you do want `uucico' to start up right away, omit the `-r'; if the call fails, the poll file will be left around to cause a later call.
For example, I use the following crontab entries locally:
45 * * * * /bin/echo /usr/lib/uucp/uucico -r1 | /bin/su uucpa 40 4,10,15 * * * /usr/bin/uux -r uunet!
Every hour, at 45 minutes past, this will check if there is any work to
be done, and, if there is, will call the appropriate system. Also, at
4:40am, 10:40am, and 3:40pm, this will create a poll file file for
`uunet', forcing the next run of uucico to call
`uunet'.
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