Re: case of printf >fifo hang in int trap

[Chet Ramey]

On 2/13/22 1:33 PM, Alex fxmbsw7 Ratchev wrote:
> it hangs, further control-c dont take action, control-z maybe in scripts in
> interactive not
> so i have, mkfifo fifo ; trap 'printf nowork>fifo' int, it hangs on it, in
> interactive the whole even makes all three key combos i know nowork,
> control c and z and \
>
> test:
>
> mkfifo ${a:=/tmp/afifo}
> trap 'printf hang >$a' int
>
> first control-c is run, the rest is hanging, displaying ^C and ^\ and ^Z
> but nothing happens

OK. What do you expect to happen?

The second SIGINT interrupts the open that gets run by the trap handler
for the first SIGINT (which hangs until someone opens the FIFO for
reading), but the signal remains trapped. You're just going to keep
trying to open the FIFO and write something to it every time you hit ^C,
which seems fairly pointless.

The SIGQUIT is always ignored.

There's no external process created, so the SIGTSTP has no effect.

In fact, the whole exercise, starting with trying to open a FIFO from a
trap handler without opening it for reading, seems pointless or worse.

--
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/