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Fast way to split a tab delimited file

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Top Forums Shell Programming and Scripting Fast way to split a tab delimited file
# 8  
Old 05-18-2006
I believe grep would do it faster than awk. Try using johnywilkins suggestion and compare the time taken.
# 9  
Old 05-18-2006
awk seems to be faster on my system.

Test with 500 records:

Code:
#! /usr/bin/ksh

print "Single task awk"
time {
    > M.txt
    > D.txt
    nawk '{
        if ($0 ~ /^M/) print $0 >"M.txt"
        else print $0 >"D.txt"
    }' test.dat
}
ls -altr M.txt D.txt

print "Two task awk"
time {
    > M.txt
    > D.txt
    nawk '/^M/' test.dat >> M.txt &
    nawk '/^D/' test.dat >> D.txt &
    wait
}
ls -altr M.txt D.txt

print "4-way awk"
time {
    > M.txt
    > D.txt
    nawk 'NR <  250000 && /^M/' test.dat >> M.txt &
    nawk 'NR >= 250000 && /^M/' test.dat >> M.txt &
    nawk 'NR <  250000 && /^D/' test.dat >> D.txt &
    nawk 'NR >= 250000 && /^D/' test.dat >> D.txt &
    wait
}
ls -altr M.txt D.txt

print "Grep"
time {
    > M.txt
    > D.txt
    grep "^M" test.dat > M.txt &
    grep "^D" test.dat > D.txt &
    wait
}
ls -altr M.txt D.txt

results:
Code:
Single task awk

real    3m12.40s
user    0m4.69s
sys     0m9.63s
-rw-r--r--   1 ... 34770850 ... D.txt
-rw-r--r--   1 ... 46222065 ... M.txt

Two task awk

real    0m14.12s
user    0m5.93s
sys     0m1.55s
-rw-r--r--   1 ... 34770850 ... D.txt
-rw-r--r--   1 ... 46222065 ... M.txt

4-way awk

real    0m16.14s
user    0m10.52s
sys     0m2.48s
-rw-r--r--   1 ... 34770850 ... D.txt
-rw-r--r--   1 ... 46222065 ... M.txt

Grep

real    0m22.70s
user    0m1.50s
sys     0m3.24s
-rw-r--r--   1 ... 34770850 ... D.txt
-rw-r--r--   1 ... 46222065 ... M.txt

# 10  
Old 05-18-2006
Quote:
Originally Posted by tmarikle
awk seems to be faster on my system.

Test with 500 records:

Code:
#! /usr/bin/ksh

print "Single task awk"
time {
    > M.txt
    > D.txt
    nawk '{
        if ($0 ~ /^M/) print $0 >"M.txt"
        else print $0 >"D.txt"
    }' test.dat
}
ls -altr M.txt D.txt

print "Two task awk"
time {
    > M.txt
    > D.txt
    nawk '/^M/' test.dat >> M.txt &
    nawk '/^D/' test.dat >> D.txt &
    wait
}
ls -altr M.txt D.txt

print "4-way awk"
time {
    > M.txt
    > D.txt
    nawk 'NR <  250000 && /^M/' test.dat >> M.txt &
    nawk 'NR >= 250000 && /^M/' test.dat >> M.txt &
    nawk 'NR <  250000 && /^D/' test.dat >> D.txt &
    nawk 'NR >= 250000 && /^D/' test.dat >> D.txt &
    wait
}
ls -altr M.txt D.txt

print "Grep"
time {
    > M.txt
    > D.txt
    grep "^M" test.dat > M.txt &
    grep "^D" test.dat > D.txt &
    wait
}
ls -altr M.txt D.txt

results:
Code:
Single task awk

real    3m12.40s
user    0m4.69s
sys     0m9.63s
-rw-r--r--   1 ... 34770850 ... D.txt
-rw-r--r--   1 ... 46222065 ... M.txt

Two task awk

real    0m14.12s
user    0m5.93s
sys     0m1.55s
-rw-r--r--   1 ... 34770850 ... D.txt
-rw-r--r--   1 ... 46222065 ... M.txt

4-way awk

real    0m16.14s
user    0m10.52s
sys     0m2.48s-rw-r--r--   1 ... 34770850 ... D.txt
-rw-r--r--   1 ... 46222065 ... M.txt

Grep

real    0m22.70s
user    0m1.50s
sys     0m3.24s-rw-r--r--   1 ... 34770850 ... D.txt
-rw-r--r--   1 ... 46222065 ... M.txt



How do you find the time taken to execute the script?
# 11  
Old 05-18-2006
I have the results like this with the same file..This is a Sunsolaris machine..

Single task awk

real 2m21.59s
user 1m11.76s
sys 0m58.18s
-rw-r--r-- 1 develop 722 May 18 13:48 M.txt
-rw-r--r-- 1 develop 3055795862 May 18 13:50 D.txt
Two task awk

real 1m4.71s
user 1m25.91s
sys 0m33.18s
-rw-r--r-- 1 develop 3055795623 May 18 13:51 D.txt
-rw-r--r-- 1 develop 722 May 18 13:51 M.txt
4-way awk

real 1m10.57s
user 2m30.03s
sys 0m45.67s
-rw-r--r-- 1 develop 722 May 18 13:52 M.txt
-rw-r--r-- 1 develop 3055795623 May 18 13:52 D.txt
Grep

real 0m29.55s
user 0m9.62s
sys 0m30.49s
-rw-r--r-- 1 develop 722 May 18 13:53 M.txt
-rw-r--r-- 1 develop 3055795623 May 18 13:53 D.txt
# 12  
Old 05-18-2006
Your grep is faster than my Sun Solaris grep by a long shot (comparatively speaking of course).
# 13  
Old 05-18-2006
This ksh script should be faster than the original...
Code:
#! /usr/bin/ksh
exec < inputfile
IFS=""
exec 3>M.out 4>D.out
while read line ; do
        if [[ $line = M* ]] ; then
                print -u3 "$line"
        else
                print -u4 "$line"
        fi
done
exit 0

# 14  
Old 05-18-2006
Thank you very much guys...I did learn a lot today!!
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