SC3032 – ShellCheck Wiki

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In POSIX sh, coproc is undefined.

Problematic code:

coproc nc 80

Correct code:

Either switch to Bash:

#!/usr/bin/env bash
coproc nc 80

or try to write your script in a POSIX compatible way using named pipes.


Your script uses a shell feature not supported by the shebang. Either rewrite the script to be portable, or change the shebang to explicitly require a shell like Bash.

There is no simple substitution for a coproc, though many use cases can be rewritten via redirection to named pipes (mkfifo).



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