Named pipes - FIFO pipes.

Postby **viking60** » 21 Jun 2014, 15:34

We have that regular pipes typically

cat /var/log/somelog.log |less

It will show you the log per page. The named pipes or FIFO (First in First Out) pipes are a container ready to receive your instructions and is a file so you have to create it:

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mkfifo berserk_pipe

To put this file in receiver mode you can simply do a

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cat berserk_pipe

Now this terminal will be "frozen" waiting for messages.
Open another terminal next to the frozen one and type:

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echo "Hi Hola Hallo!!" >>berserk_pipe

The message will turn up in the other receiving terminal and it will go back to the normal prompt

To make the receiving terminal remain in that "listening mode" you can start it with:

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tail -f berserk_pipe

As you can see the left terminal will wait for any command or message. You can send regular commands too:

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ls >> berserk_pipe

It can be useful when exchanging data between different users etc.

You can also use this in combination with SSH

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ssh berserk@10.0.0.12 "echo hallo >> berserk_pipe"

Remember berserk_pipe is just a file and you can have a look at it with:

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ls -l berserk_pipe

the output will be something like this:

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prw-r--r-- 1 berserk berserk 0 juni 21 16:15 berserk_pipe

Note the p in front it indicates that it is a pipe.

If you have started the pipe with tail -f you need to stop it with CTRL+C
The pipe file can be removed with a regular rm.

So what can this be used for? Use your imagination :-D

I will come up with a practical example later...