[Gllug] Named pipes

[Richard Jones]

On Tue, Dec 11, 2007 at 11:32:54AM +0000, Toby Waterford wrote:
> I've worked out how to use unnamed pipes and I finding them very
> useful. I may be being dim, but named pipes completely confuse me -
> are they useful? Does anyone have any advice on getting to grips with
> them?

They're not really very useful.  Very occasionally you might have,
say, a shell script where you want to use a named pipe to communicate
between two unrelated processes (unnamed pipes can only be created
where two processes are related to each other through fork(2)).  A
rather contrived example might be:

  mknod syslog-pipe p
  logger < syslog-pipe &

  [and in another shell script ...]

  echo "Log message" >> syslog-pipe

Actually that example doesn't work too well because the 'logger'
process exits after the first log message is sent.

When talking to system daemons, a common method is to communicate over
a Unix domain socket which is similar to a named pipe but uses BSD
socket calls.  See the unix(7) man page and the output of:

  netstat -a | grep ^unix

Rich.

-- 
Richard Jones
Red Hat
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