How to split a file and keep the first line in each of the pieces?

This is robhruska's script cleaned up a bit:

tail -n +2 file.txt | split -l 4 - split_for file in split_*do    head -n 1 file.txt > tmp_file    cat "$file" >> tmp_file    mv -f tmp_file "$file"done

I removed wc, cut, ls and echo in the places where they're unnecessary. I changed some of the filenames to make them a little more meaningful. I broke it out onto multiple lines only to make it easier to read.

If you want to get fancy, you could use mktemp or tempfile to create a temporary filename instead of using a hard coded one.

Edit

Using GNU split it's possible to do this:

split_filter () { { head -n 1 file.txt; cat; } > "$FILE"; }; export -f split_filter; tail -n +2 file.txt | split --lines=4 --filter=split_filter - split_

Broken out for readability:

split_filter () { { head -n 1 file.txt; cat; } > "$FILE"; }export -f split_filtertail -n +2 file.txt | split --lines=4 --filter=split_filter - split_

When --filter is specified, split runs the command (a function in this case, which must be exported) for each output file and sets the variable FILE, in the command's environment, to the filename.

A filter script or function could do any manipulation it wanted to the output contents or even the filename. An example of the latter might be to output to a fixed filename in a variable directory: > "$FILE/data.dat" for example.

This one-liner will split the big csv into pieces of 999 records, preserving the header row at the top of each one (so 999 records + 1 header = 1000 rows)

cat bigFile.csv | parallel --header : --pipe -N999 'cat >file_{#}.csv'

Based on Ole Tange's answer.(re Ole's answer: You can't use line count with pipepart)

See comments for some tips on installing parallel

You could use the new --filter functionality in GNU coreutils split >= 8.13 (2011):

tail -n +2 FILE.in | split -l 50 - --filter='sh -c "{ head -n1 FILE.in; cat; } > $FILE"'