I've been working in Learning Perl and recently got to the section on opening file handles to system commands and piping to them. I tried: 
open(COPY, "| cp") || die("Could not open COPY: $!");;
print COPY "file1 file2" || die("Could not print to COPY: $!");
close COPY || die("Could not close COPY: $!");

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This failed on close, and I learned from reading perlman:perlipc that if a command can't accept input from a pipe, it will always die on close.

My question is: is there any way to tell ahead of time whether or not the command I want to pipe to will accept my input, a more efficient test than just seeing if it dies on close? Is there a list compiled somewhere of standard Unix commands that will/won't take input from a pipe?

In reply to Piping into system commands by Vortacist

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