You need to flush the buffer after printing the headers, and before calling rrd. The easiest way is to set $| = 1 to enable autoflush, so the buffer will be flushed after each line, instead of in blocks. You should also read through Suffering from Buffering.

We're not surrounded, we're in a target-rich environment!

In reply to Re: Tricking a filename argument to use STDOUT by jasonk
in thread Tricking a filename argument to use STDOUT by fapestniegd

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