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Accepted
vikarjramun
Asked: 2018-06-02 08:29:36 +0800 CST

How to pipe all bash terminal output through command [duplicate]

  • 772

I would like to be able to pipe all bash terminal commands through a certain command (for no good reason other than to play a prank on someone). I just want to pipe the stdout of any executed command into a predetermined program without doing anything special.

For example: If that predetermined program was cowsay

echo "Hello World"

should output

 _____________
< Hello World >
 -------------
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||

How can I achieve this? (Some of the fun programs I'd like to use to play pranks on others include rev, cowsay, and lolcat)

command-line bash pipe cowsay

1 Answers

  1. Best Answer
    exec > >(COMMAND)

    Where COMMAND is rev, lolcat or other. This won't work with cowsay.

    E.g.

    bash-4.3$ exec > >(rev)
bash-4.3$ echo hello
olleh

    Explanation:

    • exec normally replaces the current shell with another process, but if you just give it a redirection like in this case, the redirection will take place for the current shell.
    • > redirect stdout
    • >(COMMAND) input into COMMAND

    Note that if you have a PROMPT_COMMAND, you should direct it to stderr to avoid the redirected stdout.

    • 7