splitting a CSV and keeping the header without intermediate files

Question

I am trying to split a dozen 100MB+ csv files into managable smaller files for a curl post.

I have managed to do it but with a lot of temporary files and IO. It's taking an eternity.

I am hoping someone can show me a way to do this much more effectively; preferably with little to no disk IO

#!/bin/sh

for csv in $(ls *.csv); do
    tail -n +2 $csv | split -a 5 -l - $RANDOM.split.
done

# chose a file randomly to fetch the header from   

header=$(ls *.csv |sort -R |tail -1 | cut -d',' -f1)

mkdir split

for x in $(/usr/bin/find . -maxdepth 1 -type f -name '*.split.*'); do
    echo Processing $x
    cat header $x >> split/$x
    rm -f $x
done

The above script may not entirely work. I basically got it working through a combination of these commands.

I decided to make the curl POST another step entirely in the case of upload failure; I didn't want to lose the data if it were all posted. But, if, say, on error from curl the data could be put into a redo folder then that can work.

#!/bin/sh

# working on a progress indicator as a percentage. Never finished.
count=$(ls -1 | wc -l 2> /dev/null | cut -d' ' -f1)

for file in $(/usr/bin/find . -maxdepth 1 -type f); do
    echo Processing $file
    curl -XPOST --data-binary @$file -H "Content-Type: text/cms+csv" $1
done

Solution

An entirely different approach would be to use GNU parallel, and use its --header and --pipe options:

cat input.csv | parallel --header : --pipe -N 10 'cat > output{#}.csv'

This will get you 11 lines in each of the files (the header line plus the ten from -n 10, except in the last file written that way).

Comments

[John1024]

This question has been cross-posted at SO: stackoverflow.com/questions/26708081/…

[Olivier Dulac]

this really looks like an XYProblem: what do you need to do? are you sure you need to do it via multiple http post? if you have access to the machine, you can scp, rsync, etc.

[chepner]

$(ls *.csv) is redundant; just use for csv in *.csv.

[Michael Finco]

@OlivierDulac -- I actually have to POST it because it has to be processed by a webservice. It's not just a straight upload.

[Michael Finco]

This looks interesting. I will have to give this a try.