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Fast way to split a tab delimited file

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# 1  
Old 05-18-2006
Fast way to split a tab delimited file

I have searched the forum and tried different options. One of the options work but is very slow. The file has millions and millions of records.

It is a TAB delimited file which contains two types of records. Metadata and Detail records.


I need to split the file into two files by looking at the first character. All records that start with 'M' go into one file and all records that start with 'D' go into another file.

The following code works but it is too slow...Is there any fast way of accomplishing it?


while read line
char=`echo "$line" | cut -c1`
if [ "$char" = "M" ]; then
echo "$line" >> M.txt
echo "$line" >> D.txt
done < head10000.out

exit 0

Any help would be appreciated.

Thank You,
# 2  
Old 05-18-2006
'Awk' will be the quick way to do this. Unfortunately I'm not an expert in the syntax, but from experience its much faster that a standard shell script.

# 3  
Old 05-18-2006
Thank you Helen...

I believe something like this would work..

awk -v logfile=${1:-"stdin"} '{ print > logfile"-"$1 }' "$1"

But it is throwing an error...
awk: syntax error near line 1
awk: bailing out near line 1

Any awk experts out there to resolve this situation.
# 4  
Old 05-18-2006
How fast does it need to be ? Is a simple grep faster than looping within a script ?

grep "^M" head10000.out > M.txt
grep "^D" head10000.out > D.txt
# 5  
Old 05-18-2006
awk '{
    if ( $0 ~ /^M/) print >"M.txt"
    else print >"D.txt"
}' head10000.out

# 6  
Old 05-18-2006
Thank you very much....

There are 13019984 records in the file.

5 M records and the rest of them are D records.

It took 10-11 mins to run the awk program...Is this a good standard?

Thanks again for all the help!
# 7  
Old 05-18-2006
21,700 records per second seems good to me.

You may be able to split the work into two tasks and improve performance.
awk '/^M/' head10000.out > M.txt &
awk '/^D/' head10000.out > D.txt &

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