How to flush perl’s print buffer?

Sometimes, if you put a print statement inside of a loop that runs really really quickly, you won’t see the output of your print statement until the program terminates; sometimes, you don’t even see the output at all.

The solution to this problem is to “flush” the output buffer after each print statement; this can be performed in perl with the following command:

$| = 1;

Two examples to understand how it works:

$| = 1;
for ($i=0; $i<10; $i++) {
print “=”;
sleep 1;
}
print “\n”;

$| = 0;
for ($i=0; $i<10; $i++) {
print “=”;
sleep 1;
}

Also, printing “\n” flushes the buffer, which you can verify by modifying the last print statement from “=” to “=\n”.

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Reference:
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