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Splitting a file into parts

Posted on 2007-03-27
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Last Modified: 2010-04-20
I have a file which I would like to split into certain number of parts. I
wrote a script using the split command. For example, if there are 19 lines
and I pass in a parameter of n=4, I would like the file to be split into
4 parts of 5,5,5,4 parts. I have looked into csplit but it doesn't seem to
be doing what I want it to do.
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Question by:soccerplayer
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amit_g earned 500 total points
ID: 18803713
Try this ...

n=4
split -l $((($(cat YourFileName | wc -l) + $n) / $n))
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by:soccerplayer
ID: 18816277
This does not work. I ran this running last night and it was still running this morning.
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Expert Comment

by:amit_g
ID: 18818074
What do you mean that it is still running since last night? Is the file you are splitting huge? Even then whole night is way too long. In any case you should have first tested it on a smaller file.
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Expert Comment

by:crovaxy
ID: 18822383
Use the 'dd' utility.

For a file with 100 bytes use:

dd if=/path/to/file_to_split of=/path/to/file_part1 count=25 bs=1
dd if=/path/to/file_to_split of=/path/to/file_part2 count=25 bs=1 skip=25
dd if=/path/to/file_to_split of=/path/to/file_part3 count=25 bs=1 skip=50
dd if=/path/to/file_to_split of=/path/to/file_part4 count=25 bs=1 skip=75

Check out the 'dd' man page for more information.
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Expert Comment

by:crovaxy
ID: 18822419
Ops, you want to split by lines... sorry!

Then you can use something like this:

filename=test_part2.txt
lines=4
total_lines=`cat $filename | wc -l`;
offset=4

while :; do
        if [ $offset -gt $total_lines ]; then
                echo "PART #"
                cat $filename | head -n $offset | tail -n $[$total_lines%$lines];
                break;
        else
                echo "PART #"
                cat $filename | head -n $offset | tail -n $lines;
                offset=$[$offset+$lines];
        fi
done
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Author Comment

by:soccerplayer
ID: 18831162
crovaxy, thank your for your response. I know that it can be done in a script but I was wondering if there was any way to do it using the split or csplit commands.
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Expert Comment

by:amit_g
ID: 18831200
It can be. The command I posted is tested. You need to explain what did not work and how you used it.
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Expert Comment

by:crovaxy
ID: 18833779
the amit_g answer is correct. You can parse the file using that command. You're problem, probably, is that you're not passing the YourFileName argument to the split command. The YourFileName in the amit_g answer is just for the 'cat' command which will be parsed by 'wc' to achieve the total lines on the file... it is not the filename argument to the split command itself.

Eg:

n=4
split -l $((($(cat YourFileName | wc -l) + $n) / $n)) YouFileName
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