Andy T Andy T - 2 months ago 14
Linux Question

why doesn't watch work when piping the output of fortune into cowsay

cowsay is a silly linux tool for displaying a cow saying given text in the terminal.

$ cowsay hello


fortune is a silly linux too for displaying a "random" quote in the terminal.

$ fortune


Both of these commands can be repeatedly ran in the terminal using watch e.g.

$ watch cowsay hello
$ watch fortune


Additionally these two commands can be combined so the cow says "random" quotes. By piping the output of fortune into cowsay.

$ fortune | cowsay


However a combination of the use of watch and piping the output of fortune into cowsay doesn't do anything.... i.e. hangs until the process is ended

$ watch fortune | cowsay


Does anyone know why?

Answer

With watch fortune | cowsay you are piping the output of watch fortune into cosway. You want to watch the value of fortune piped to cosway so you should quote it so watch will get the whole command to execute as

watch 'fortune | cowsay'
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