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Two named PIPEs (PIPE_in/PIPE_out) connected with `tail -f` | String sent to PIPE_in doesn't reach PIPE_out



The 2019 Stack Overflow Developer Survey Results Are InProblem with pipes. Pipe terminates when reader doneWhat are the difference between those four commands (fifo, process substitution, redirection…)Tailing log files in two different hostsNamed pipes: several experiments leads to confusionHow to forward between processes with named pipes?Unbuffered socat command to connect serial ports in remote machines and log the dataWrite to stdin of running process on occasionProvide Data Via Named PipeBroken pipes! Problem with using named pipes to link together 2 standalone programsgrep --exclude option doesn't always skip named pipes



.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;








1















1.Create named PIPEs, pipe_in and pipe_out by running:



$ mkfifo pipe_in
$ mkfifo pipe_out


2.Connect pipe_in to pipe_out:



TERM0: $ tail -f pipe_in > pipe_out


3.Send string hello world! to pipe_in and expect it to arrive at pipe_out:



TERM1: $ tail -f pipe_out
TERM2: $ echo "hello world!" > pipe_in


I can only see the string arriving at pipe_out if I kill command in 2..
It seems to be a buffering issue so I decided to run all commands above with stdbuf -i0 -e0 -o0 <command> but it didn't work.










share|improve this question



















  • 1





    Good point, @Jeff Schaller. I have just deleted that question. I find this one, here, more fundamental. As soon as I solve this one I will likely be able to solve the other one too.

    – fmagno
    Mar 11 at 16:41


















1















1.Create named PIPEs, pipe_in and pipe_out by running:



$ mkfifo pipe_in
$ mkfifo pipe_out


2.Connect pipe_in to pipe_out:



TERM0: $ tail -f pipe_in > pipe_out


3.Send string hello world! to pipe_in and expect it to arrive at pipe_out:



TERM1: $ tail -f pipe_out
TERM2: $ echo "hello world!" > pipe_in


I can only see the string arriving at pipe_out if I kill command in 2..
It seems to be a buffering issue so I decided to run all commands above with stdbuf -i0 -e0 -o0 <command> but it didn't work.










share|improve this question



















  • 1





    Good point, @Jeff Schaller. I have just deleted that question. I find this one, here, more fundamental. As soon as I solve this one I will likely be able to solve the other one too.

    – fmagno
    Mar 11 at 16:41














1












1








1








1.Create named PIPEs, pipe_in and pipe_out by running:



$ mkfifo pipe_in
$ mkfifo pipe_out


2.Connect pipe_in to pipe_out:



TERM0: $ tail -f pipe_in > pipe_out


3.Send string hello world! to pipe_in and expect it to arrive at pipe_out:



TERM1: $ tail -f pipe_out
TERM2: $ echo "hello world!" > pipe_in


I can only see the string arriving at pipe_out if I kill command in 2..
It seems to be a buffering issue so I decided to run all commands above with stdbuf -i0 -e0 -o0 <command> but it didn't work.










share|improve this question
















1.Create named PIPEs, pipe_in and pipe_out by running:



$ mkfifo pipe_in
$ mkfifo pipe_out


2.Connect pipe_in to pipe_out:



TERM0: $ tail -f pipe_in > pipe_out


3.Send string hello world! to pipe_in and expect it to arrive at pipe_out:



TERM1: $ tail -f pipe_out
TERM2: $ echo "hello world!" > pipe_in


I can only see the string arriving at pipe_out if I kill command in 2..
It seems to be a buffering issue so I decided to run all commands above with stdbuf -i0 -e0 -o0 <command> but it didn't work.







pipe fifo mkfifo






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Apr 7 at 14:47









Rui F Ribeiro

42k1483142




42k1483142










asked Mar 11 at 16:27









fmagnofmagno

82




82







  • 1





    Good point, @Jeff Schaller. I have just deleted that question. I find this one, here, more fundamental. As soon as I solve this one I will likely be able to solve the other one too.

    – fmagno
    Mar 11 at 16:41













  • 1





    Good point, @Jeff Schaller. I have just deleted that question. I find this one, here, more fundamental. As soon as I solve this one I will likely be able to solve the other one too.

    – fmagno
    Mar 11 at 16:41








1




1





Good point, @Jeff Schaller. I have just deleted that question. I find this one, here, more fundamental. As soon as I solve this one I will likely be able to solve the other one too.

– fmagno
Mar 11 at 16:41






Good point, @Jeff Schaller. I have just deleted that question. I find this one, here, more fundamental. As soon as I solve this one I will likely be able to solve the other one too.

– fmagno
Mar 11 at 16:41











2 Answers
2






active

oldest

votes


















2














tail only outputs the last n lines of a file/stream. While you are still generating lines, it can not know which are the last n.



Have you tried something like cat?






share|improve this answer























  • It is interesting though that the tail from one pipe to the other works as expected :)

    – gmagno
    Mar 11 at 18:43



















0














Please refer to @ctrl-alt-delor's answer for the reason why it doesn't work. But you can still achieve the same purpose with cat:



enter image description here






share|improve this answer

























  • It is very interesting that it works on your setup. On my setup it doesn't. I am running this on OSX, btw - not sure if it should make any difference, though... Altough, if I replace both tail commands by cat it all works fine.

    – fmagno
    Mar 12 at 10:34












  • exactly, that is also puzzling me...

    – gmagno
    Mar 12 at 11:37











Your Answer








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2 Answers
2






active

oldest

votes








2 Answers
2






active

oldest

votes









active

oldest

votes






active

oldest

votes









2














tail only outputs the last n lines of a file/stream. While you are still generating lines, it can not know which are the last n.



Have you tried something like cat?






share|improve this answer























  • It is interesting though that the tail from one pipe to the other works as expected :)

    – gmagno
    Mar 11 at 18:43
















2














tail only outputs the last n lines of a file/stream. While you are still generating lines, it can not know which are the last n.



Have you tried something like cat?






share|improve this answer























  • It is interesting though that the tail from one pipe to the other works as expected :)

    – gmagno
    Mar 11 at 18:43














2












2








2







tail only outputs the last n lines of a file/stream. While you are still generating lines, it can not know which are the last n.



Have you tried something like cat?






share|improve this answer













tail only outputs the last n lines of a file/stream. While you are still generating lines, it can not know which are the last n.



Have you tried something like cat?







share|improve this answer












share|improve this answer



share|improve this answer










answered Mar 11 at 17:03









ctrl-alt-delorctrl-alt-delor

12.4k52662




12.4k52662












  • It is interesting though that the tail from one pipe to the other works as expected :)

    – gmagno
    Mar 11 at 18:43


















  • It is interesting though that the tail from one pipe to the other works as expected :)

    – gmagno
    Mar 11 at 18:43

















It is interesting though that the tail from one pipe to the other works as expected :)

– gmagno
Mar 11 at 18:43






It is interesting though that the tail from one pipe to the other works as expected :)

– gmagno
Mar 11 at 18:43














0














Please refer to @ctrl-alt-delor's answer for the reason why it doesn't work. But you can still achieve the same purpose with cat:



enter image description here






share|improve this answer

























  • It is very interesting that it works on your setup. On my setup it doesn't. I am running this on OSX, btw - not sure if it should make any difference, though... Altough, if I replace both tail commands by cat it all works fine.

    – fmagno
    Mar 12 at 10:34












  • exactly, that is also puzzling me...

    – gmagno
    Mar 12 at 11:37















0














Please refer to @ctrl-alt-delor's answer for the reason why it doesn't work. But you can still achieve the same purpose with cat:



enter image description here






share|improve this answer

























  • It is very interesting that it works on your setup. On my setup it doesn't. I am running this on OSX, btw - not sure if it should make any difference, though... Altough, if I replace both tail commands by cat it all works fine.

    – fmagno
    Mar 12 at 10:34












  • exactly, that is also puzzling me...

    – gmagno
    Mar 12 at 11:37













0












0








0







Please refer to @ctrl-alt-delor's answer for the reason why it doesn't work. But you can still achieve the same purpose with cat:



enter image description here






share|improve this answer















Please refer to @ctrl-alt-delor's answer for the reason why it doesn't work. But you can still achieve the same purpose with cat:



enter image description here







share|improve this answer














share|improve this answer



share|improve this answer








edited Mar 11 at 18:33

























answered Mar 11 at 18:24









gmagnogmagno

1013




1013












  • It is very interesting that it works on your setup. On my setup it doesn't. I am running this on OSX, btw - not sure if it should make any difference, though... Altough, if I replace both tail commands by cat it all works fine.

    – fmagno
    Mar 12 at 10:34












  • exactly, that is also puzzling me...

    – gmagno
    Mar 12 at 11:37

















  • It is very interesting that it works on your setup. On my setup it doesn't. I am running this on OSX, btw - not sure if it should make any difference, though... Altough, if I replace both tail commands by cat it all works fine.

    – fmagno
    Mar 12 at 10:34












  • exactly, that is also puzzling me...

    – gmagno
    Mar 12 at 11:37
















It is very interesting that it works on your setup. On my setup it doesn't. I am running this on OSX, btw - not sure if it should make any difference, though... Altough, if I replace both tail commands by cat it all works fine.

– fmagno
Mar 12 at 10:34






It is very interesting that it works on your setup. On my setup it doesn't. I am running this on OSX, btw - not sure if it should make any difference, though... Altough, if I replace both tail commands by cat it all works fine.

– fmagno
Mar 12 at 10:34














exactly, that is also puzzling me...

– gmagno
Mar 12 at 11:37





exactly, that is also puzzling me...

– gmagno
Mar 12 at 11:37

















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