[BusyBox 0000758]: grep extremely slow

[bugs at busybox.net]

The following issue has been SUBMITTED. 
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http://busybox.net/bugs/view.php?id=758 
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Reported By:                rfelker
Assigned To:                BusyBox
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Project:                    BusyBox
Issue ID:                   758
Category:                   Other
Reproducibility:            always
Severity:                   major
Priority:                   normal
Status:                     assigned
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Date Submitted:             02-28-2006 00:24 PST
Last Modified:              02-28-2006 00:24 PST
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Summary:                    grep extremely slow
Description: 
time ./busybox grep a.*b ~/Mail/saved > /dev/null
real    0m19.583s
user    0m19.337s
sys     0m0.097s

time grep a.*b ~/Mail/saved > /dev/null
real    0m0.379s
user    0m0.283s
sys     0m0.083s

This is because the busybox version insists on recompiling the regex over
and over on each line. Fixing it is a matter of just calling regcomp once
and keeping the regex. It's trivial for the case of only one pattern, but
requires a tradeoff between memory and performance for the case of many
patterns.
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Issue History 
Date Modified   Username       Field                    Change               
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02-28-06 00:24  rfelker        New Issue                                    
02-28-06 00:24  rfelker        Status                   new => assigned     
02-28-06 00:24  rfelker        Assigned To               => BusyBox         
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