Re: ftrig pipe naming convention

From: Laurent Bercot <>
Date: Sun, 18 Sep 2022 20:38:27 +0000

>I wonder what is the reason behind the naming convention? What is the
>downside of simply writing to any present fifo file ?

  It could work like you're suggesting. But :

  - checking the type of a file is an additional fstat() system call
  - there may be reasons in the future to store other files in the
fifodir that do not receive the event
  - it is nice to detect stale fifos, if any, and delete them as soon
as you can (#L39), and you don't want to delete unrelated files
  - but most importantly: creating a fifo in a fifodir that allows you to
receive events without a race condition, which is the whole point of the
ftrig library, is slightly more complex to do safely than just "mkfifo
event/foobar", and I don't want people to think that this is the API.
No, the API is ftrigr_subscribe(), and everything under it is
implementation details. Restricting the naming is a way of ensuring
(as much as possible) that the fifos were indeed created by the
appropriate programs.

  Don't create fifos willy-nilly in a fifodir, and since you found the
naming convention, don't use it to work around the check to create your
fifos outside of ftrigr_subscribe(). If you do, it will work, until the
time when it doesn't, and it will be a complete PITA to debug.

Received on Sun Sep 18 2022 - 22:38:27 CEST

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