Bash: outputting a pipe to a background process?

Question

Bash: outputting a pipe to a background process?

I would like to put a process in the background and then pass data to it multiple times. For example:

cat &                    # The command I want to write into
cat_pid=$!               # Getting the process id of the cat process

echo hello | $cat_pid    # This line won't work, but shows what I want to
                         #   do: write into the stdin of the cat process

So I have a PID, how can I write to this process? I would be open to starting the cat process in a different way.

Also, I am on a Mac so I cannot use /proc

:(

+3

unix bash sh pipe macos

Christopher shroba Jul 14 At 21:01

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2 answers

mkfifo .pipe
cat < .pipe &
echo hello > .pipe

+2

Jakuje Jul 14 15 at 21:14

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John1024 · Accepted Answer · 2015-07-14T21:15:51+0000

First create a channel:

$ mkfifo pipe

Second, start your feline process with input from the pipe:

$ cat <pipe &
[1] 4997

Now send data to the channel:

$ echo "this is a test" >pipe
$ this is a test

Bash: outputting a pipe to a background process?

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