Print/Tee to console without passing output to pipe

Question

Is there a way to print or tee one thing to the console and still pass something else through to the next pipe? Something like:

echo dog | printOrWhatnot "PUTTING MY THING DOWN" | sed 's/dog/cat/g' | printOrWhatnot "FLIP IT"|rev

that would result in:

PUTTING MY THING DOWN
FLIP IT
tac

EDIT: This should also work with multiline input:

printOrWhatNot() {...}

seq 10 30 |printOrWhatNot searching for 3s | grep 3

would output

searching for 3s
13
23
30

Lars' answer seemed to only pass along the first input (here it would be 10)

Also ideally the output would come inline during processing which wasn't what I was seeing with Glen's answer. So

seq 10 30 |tee /dev/tty |printOrWhatNot searching for 3s | grep 3

would make for:

10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
searching for 3s
13
23
30

Answer 1

I'm not aware of any standard command for this purpose, but it's easy enough to craft one of your own in a little shell script. Create the following, make it executable, and add its location to your PATH.

Edit -- updated to handle multi-line standard input, and to handle spaces in the input.

printOrWhatnot:

 #!/bin/bash
 # printOrWhatnot script, to re-pipe stdin, while echoing something else via stderr

 # read stdin (possibly multi-lined) into $my_array[]:
 while read -t 1  piped
 do
    my_array=("${my_array[@]}" "$piped")
 done

 # echo the supplied arguments by sending them to stderr:
 echo "$@" 1>&2

 # now spew $my_array[], line by line, to any further processing:
 arrayLen=${#my_array[@]}
 for (( i=0; i<$arrayLen; i++ ));
 do
    echo ${my_array[$i]}
 done

Now it should work just as you suggested:

 myhost> echo dog | printOrWhatnot "PUTTING MY THING DOWN" | sed 's/dog/cat/g' | printOrWhatnot "FLIP IT"|rev
 PUTTING MY THING DOWN
 FLIP IT
 tac

Answer 2

You need to send your message to a different file descriptor than stdout, and just dump stdin to stdout untouched:

printOrWhatnot() { echo "$@" >&2; cat -; }

If you need your messages to (eventually) appear on stdout, change rev to rev 2>&1 or wrap your pipeline in braces:

{
    echo dog | 
    printOrWhatnot "PUTTING MY THING DOWN" | 
    sed 's/dog/cat/g' | 
    printOrWhatnot "FLIP IT" |
    rev
} 2>&1