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Using the always-recommended use strict; use warnings; reveals one problem with your code:

Bareword "WNOHANG" not allowed while "strict subs" in use

Another is that only the parent process should wait for the child process; if doesn't make any sense to wait for anything in the child.

In addition, doing a loop with non-blocking waitpid is useless; a single call to a blocking waitpid makes more sense. Or if you have only one child process, wait is even simpler.

Finally, afer the fork there are two writers; one in the child, one in the parent process. You need to close the one in the writer too:

#!/usr/bin/perl # always uses these; use strict; use warnings; # and detect errors use autodie; pipe(READER, WRITE); my $pid =fork(); if ($pid) { print "In parent\n"; close WRITE; my $val1 = 100; while(my $num = <READER>) { print "in while; $num\n"; } close(READER); wait; } else { print "In child\n"; my $val2 = 150; print WRITE "$val2\n"; close(WRITE); print "Child closed write\n"; }

In reply to Re: interprocess communication by moritz
in thread interprocess communication by mevans

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