named pipes

lamtab · 12-06-2007, 02:34 PM

Hi all! I was wondering if someone could give me an example of the usage of named pipes for communication of father with multiple children processes in c code. Thanks in advance

chrism01 · 12-06-2007, 04:37 PM

1st result from google: http://developers.sun.com/solaris/ar...med_pipes.html
google is your friend...

lamtab · 12-07-2007, 01:32 AM

I'm looking for a parent-multiple children example. I have an example similar to that. thx anyway

matthewg42 · 12-07-2007, 02:16 AM

Consider this:

Code:

#!/bin/bash

mkfifo fifo_one
mkfifo fifo_two

# create infinite input to fifos for illustration...
yes |sed 's/y/this is one/' | nl > fifo_one &
yes |sed 's/y/this is two/' | nl > fifo_two &

n=1
while [ $n -le 3 ]; do
        read -u 3 one_data
        read -u 4 two_data
        echo "$n  from fifo_one: \"$one_data\"; from fifo_two: \"$two_data\""
        let n+=1
done 3< fifo_one 4< fifo_two

# kill backgrounded processes
kill -9 %1
kill -9 %2

# wait will they're dead
wait

# clean up fifos
rm -f fifo_one fifo_two

matthewg42 · 12-07-2007, 02:17 AM

Oh, C code... Doh!

bigearsbilly · 12-07-2007, 03:10 AM

you are better off using sockets,
no more difficult to use and then you can also
distribute your app over a network.

maybe

lamtab · 12-07-2007, 07:40 AM

I know i can use sockets but i have to use fifos

bigearsbilly · 12-07-2007, 07:47 AM

well, it's easy, make a fifo
one process opens it for reading one for writing.
just like ordinary files.

e.g: even easier
open two xterms.

term 1

Code:

mkfifo
cat FIFO

term 2

Code:

cat > FIFO
... start typing here ...

lamtab · 12-07-2007, 08:44 AM

thx man but i want c code and communication between father and his 3 children

bigearsbilly · 12-07-2007, 08:58 AM

well, that is an example of how simple it is if you can do it with shell.

is the communication two way or one way?
well assume it's two way you must have two FIFOs per pair,
parents read/write child write/read which is 6 pipes.
but then the parent will probly need to use select to check which is ready.
(A pipe can only connect with ONE reader and ONE writer at a time)

or, you could have one pair of FIFOs and say use the PID of the child as an
IP address as it were to prepend each message,
simpler solution.

is this homework?

lamtab · 12-07-2007, 10:16 AM

Didnt know about select i'll try it. No it's not homework just learning about fifos

bigearsbilly · 12-10-2007, 03:48 AM

ok, no offence.

an interesting use for a FIFO often seen in books, is for your
mail .signature file (if this applies).
you replace it with a FIFO and a serving process that gives a
random quote (often the fortune program) every time the
FIFO is read, nifty eh?

you might like to try it.

lamtab · 12-11-2007, 10:44 AM

no offense taken. thank you