CODEWITHSUNDEEP
shellpipeipcwireshark
hr0m
hr0m

Reputation: 2805

Detach from named pipe without terminating source program

Given two programs A and B. A produces output. B consumes input. On Linux you can connect them with A | B.

Alternatively, if I want to split the execution of those programs, i can use a named pipe:

mkfifo pipe
A > pipe &
B < pipe &

However if I terminate B, A gets also killed.

Is there a way to connect A to B, while restarting B multiple times? It is not important that B loses data (e.g. during being killed in the following example), while not running. Following would be my goal, but it does not work:

mkfifo pipe
A > pipe &
B > pipe &
kill B
B > pipe &

Why do I need this?

In my case A is the JSON output from Wireshark and i am developing B to parse the correct data. I would like to do it interactively but for that i need Wireshark (or tshark) to continue sending data.

I am aware of possible duplicates with this and that, however my question is different. I did not forget to redirect A to somewhere else, I can prepare it beforehand.

Upvotes: 2

Views: 253

Answers (1)

oguz ismail
oguz ismail

Reputation: 50750

A receives a SIGPIPE the moment B terminates. A workaround is:

exec 3<>pipe
A >&3 &
B <&3 &

This way the kernel won't signal A when B dies as the fifo was opened for reading by another process; i.e B wasn't the last process reading from it.

Upvotes: 2

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