Redirect the output of one command to more than one command

Question

I know that using a pipe I can redirect the output of a command to another command:

cmd1 | cmd2

Also when I use something like:

cmd1 | cmd2 | cmd3

the second pipe make that cmd3 to take the output of cmd2. My question is: is it possible to make cmd3 to take the output of cmd1?

Answer 1

You can use tee:

cmd1 | tee >(cmd2) >(cmd3)

or pee:

cmd1 | pee "cmd2" "cmd3"

tee should be installed by default in all Unix like systems, while pee can be found in moreutils package.

Answer 2

You can do it with tee and named pipes:

 $ fifo=/tmp/1to3
 $ mkfifo $fifo
 $ cmd1 | tee $fifo | cmd2 & cmd3 <$fifo

Answer 3

IF guaranteed order of execution of cmd2 and cmd3 and/or guaranteed order of their output (if any) are a concern, using process substitution (>(...)) or named pipes (FIFOs) is NOT an option.
Instead:

• Use the pee utility as demonstrated in Radu Radeanu's answer, if installing it is an option (and it's available for your platform).

• Otherwise, use a temporary file as follows:

cmd1 | { f=$(mktemp) && cat >$f; cmd2 <$f; cmd3 <$f; rm $f; }

^{(On OSX, use mktemp -t tmp instead of just mktemp; mktemp -t XXXX would work on both platforms).}

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