I have a simple problem and a solution that is too simple..

I have a simple fixed length file of about 1GB in size, with records 1001 bytes long. However, a few lines are the wrong size. I want to separate them into two files, good.txt and bad.txt.

I started with the following, which works on a small test file perfectly:

perl -ne 'print and next if length($_)==1001; print STDERR $_' suspect.txt > goodrecs.txt 2> badrecs.txt

The problem seems to be that there is a bad record in the real-world file that is around 250MB long and near the end. So it looks like Perl is thrashing for hours trying to read that line into $_. (In Windows XP, the memory usage bounces up and down 100MB every few seconds, and it's reading about 8k per second.)

I tried adding BEGIN {$|++} so at least it'd flush the buffer to the goodrecs.txt before thrashing, but it still stops writing mid-record. (But it does write a little more.)

What can I do? And what is a general solution? :)

Any guidance is appreciated, oh Perl monks.

In reply to Thrashing on very large lines by chr1so

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