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linuxbashhttp-redirectpipetee

transform stream sent to a file by tee


I want to redirect the stdout and stderr of a stream both to the screen and a file. For that I'm using the tool tee. However, before that stream goes to the file, I want to transform it using a pipe. So far, I have only managed to transform the stream that goes to stdout.

Example:

echo 'hello' | tee output.txt | tr 'h' 'e'

=> this will output eello to stdout and save hello to output.txt

However what I want is to print hello to stdout and save eello to output.txt.

Note: Changing the input stream is not an option for my problem.


Solution

  • With bash:

    echo 'hello' | tee >(tr 'h' 'e' > output.txt)
    

    With bash and Linux:

    echo 'hello' | tee /proc/$$/fd/255 | tr 'h' 'e' > output.txt
    

    See: What is the use of file descriptor 255 in bash process