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LC_CTYPE=C speeds 'grep a' 800 times
From: |
Dan Jacobson |
Subject: |
LC_CTYPE=C speeds 'grep a' 800 times |
Date: |
Sat, 16 Aug 2003 03:04:54 +0800 |
User-agent: |
Gnus/5.1002 (Gnus v5.10.2) Emacs/21.3 (gnu/linux) |
Gentlemen, what's the deal in that the shorter the regexp, the longer
the grep time?
# time zcat /var/log/syslog.*.gz|grep . > /dev/null
real 0m28.991s
user 0m28.990s
sys 0m0.000s
# time zcat /var/log/syslog.*.gz|grep fetchmail > /dev/null
real 0m6.556s
user 0m6.550s
sys 0m0.000s
# time zcat /var/log/syslog.*.gz|grep a > /dev/null
real 0m28.200s
user 0m28.190s
sys 0m0.010s
# grep --version
grep (GNU grep) 2.5.1
Holy s*it batman, it was all a plot by the elite westerners to slow
down other races' computers!
# time zcat /var/log/syslog.*.gz|LC_CTYPE=C grep . > /dev/null
real 0m0.035s
user 0m0.030s
sys 0m0.000s
# time zcat /var/log/syslog.*.gz|LC_CTYPE=C grep fetchmail > /dev/null
real 0m0.030s
user 0m0.030s
sys 0m0.000s
# time zcat /var/log/syslog.*.gz|LC_CTYPE=C grep a > /dev/null
real 0m0.035s
user 0m0.020s
sys 0m0.020s
Normally I have
LANG=zh_TW.Big5
LC_CTYPE=zh_TW.Big5
Anyway, fgrep only helped in the "." case, 16 sec vs. 28.
Anyway, 800 times!
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