Re: bash - pipe

In message <48dc9029$0$1075$4fafbaef@xxxxxxxxxxxxxxxxxxx>, Antonio Macchi
wrote:

hi

I can't understand this pipe-behavior..

------------------

$ mkfifo fifo

$ echo 123 > fifo &
[1] 7535

$ echo 456 > fifo &
[2] 7536

$ read -n3 < fifo
[1]- Done echo 123 >fifo
[2]+ Done echo 456 >fifo

$ read -n3 < fifo

(hang! - empty pipe)


--------------------


More than one process can append his output to a pipe

but...

Only one process can read a pipe
When he has fished, no more processes can read remaining-data

This certainly works:

ldo@theon:~> mkfifo /tmp/fifo
ldo@theon:~> echo 123 >/tmp/fifo &
[1] 25790
ldo@theon:~> echo 456 >/tmp/fifo &
[2] 25791
ldo@theon:~> cat </tmp/fifo
456
123
[1]- Done echo 123 > /tmp/fifo
[2]+ Done echo 456 > /tmp/fifo

Trying to reproduce your example:

ldo@theon:~> echo 123 >/tmp/fifo & echo 456 >/tmp/fifo &
[1] 25800
[2] 25801
ldo@theon:~> read -n3 </tmp/fifo; echo $REPLY
123
bash: echo: write error: Broken pipe
ldo@theon:~>
[1]- Done echo 123 > /tmp/fifo
[2]+ Exit 1 echo 456 > /tmp/fifo

The second echo died as soon as the input end of the pipe was closed.
.

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