I want to split sourcefile.txt which contains 10000 lines, (increasing everyday) into 30 equal files. I have directories called prog1 to prog30 and I would like to save split the file into these directories with the same filename. For example /prog1/myfile.txt, /prog2/myfile.txt to /prog30/myfile.txt.

Here is my bash script called divide.sh runs in prog directory

totalline=$(wc -l < ./sourcefile.txt)   
divide="$(( $totalline / 30 ))"   
split --lines=$divide $./prog1/myfile.txt    
exit 1

6 Answers 6


# assuming the file is in the same folder as the script
# assuming the folder called "output" is in the same folder
# as the script and there are folders that have the patter
# prog01 prog02 ... prog30
# create that with mkdir output/prog{01..30} 


# split 
# -n -> 30 files
# $OUTPUT_FILE_FORMAT -> should start with this pattern
# --numeric-suffixes=1 -> end of file name should start from 01 
split -n 30 $INPUT $OUTPUT_FILE_FORMAT --numeric-suffixes=1

# move all files to their repective directories
for i in {01..30} 
    mv $OUTPUT_FILE_FORMAT$i $OUTPUT_FOLDER/prog$i/myfile.txt

echo "done :)"


The split command is more than enough for this task. However the solution here requires you to make your folder names start from prog01 and not prog1


The awk only solution (N here equals 30 files):

awk 'BEGIN{ cmd="wc -l <sourcefile.txt"; cmd|getline l; l=int((l+29)/30); close(cmd) } 
    NR%l==1{trgt=sprintf("prog%d",((++c)))}{print >trgt"/myfile.txt"}' sourcefile.txt

Or let shell run and return the number of lines in sourcefile.txt and pass to awk as suggested by jthill.

awk 'NR%l==1{trgt=sprintf("prog%d",((++c)))}{print >trgt"/myfile.txt"}' 
    l=$(( ($(wc -l <sourcefile.txt)+29)/30 )) sourcefile.txt
  • 1
    I think I like this one best. I'd do the lines-per-file calc on the command line, though: awk 'NR%perfile==1...' perfile=$(( ($(wc -l <sourcefile.txt)+29)/30 )) sourcefile.txt since awk's piping is, erm, awkward ...
    – jthill
    Commented Oct 30, 2017 at 14:48
  • @jthill Thanks, very good, I have moved your suggested command into my answer, thank you ^_^ Commented Nov 16, 2017 at 4:53

split + bash solution:

lines=$(echo "t=$(wc -l ./sourcefile.txt | cut -d' ' -f1); d=30; if(t%d) t/d+1 else t/d" | bc)
split -l $lines ./sourcefile.txt "myfile.txt" --numeric-suffixes=1

for f in myfile.txt[0-9]*; do 
    dir_n="prog"$(printf "%d" "${f#*txt}")  # constructing directory name
    mv "$f" "$dir_n/myfile.txt"

Assuming that you already have folders called prog1 to prog30 (as you mentioned)

  • lines - contains the integer number of lines per output file

    • t - total number of lines of file ./sourcefile.txt
    • d=30 is a divider
  • --numeric-suffixes=1 - split's option, tells to use numeric suffixes starting at 1


Sed version for fun:

lines=$(wc -l <sourcefile.txt)
perfile=$(( (lines+29)/30 ))     # see https://www.rfc-editor.org/rfc/rfc968.txt
sed -nf- sourcefile.txt <<EOD
$(while let $((last<lines)); do 
        mkdir -p prog$((last/perfile+1))
        echo $((last+1)),$((last+perfile)) w prog$((last/perfile+1))/myfile.txt
        : $((last+=perfile))
  • Surprisingly this solution is worked with 1.500.000 files. I did try two files which contains 10.000 and other file 1.500.000 lines. although split function good for less than 10000 lines. It is messed up after 35.000. be careful last line it is splitting middle of line. I spend nearly one day just trying to find what is wrong with the split saved file, after deleting last line which cuts middle of sentence, it does work. On the other hand I use sed answer for 1.5M files, It perfectly cut without loosing any lines. I highly recommend to use sed for large lines. I didn't try awk solution.
    – danone
    Commented Oct 31, 2017 at 13:30


  1. count the lines in file and divide by 30 lines = cat ${file} | wc -l

  2. get the amount of files you need (bash will round it up to an integer) numOfFiles = ${lines} / 30

  3. use split to divide the file split -l ${lines} -d --additional-suffix=-filename.extension ${file}

Expected result

x01-filename.extension, x02-filename.extension... xN-filename.extension

Wrap it into a for loop to process more than one file at a time

for FILE in $(find ${pathToWorkingDir} -type f -name "filename.extension")
    split -l ${lines} -d --additional-suffix=-filename.extension ${file}
    if [ $? -eq 0 ]; then
        echo "${file} splitted file correctly"
        echo "there was a problem splitting ${file}"
        exit 1 #we exit with an error code
exit 0 #if all processed fine we exit with a success code

Parallelized with GNU Parallel:

parallel -j30 -a sourcefile.txt --pipepart --block -1 'mkdir -p prog{#};cat >prog{#}/myfile.txt'

This will run 30 jobs in parallel, splitting sourcefile.txt into one part per job (i.e. 30) and give the parts to cat that saves into prog{jobnumber}/myfile.txt.

Running in parallel GNU Parallel needs filehandles. This means that if you do not change the number of available file handles, you can at most run around 250 jobs in parallel.

But you can easily split into more blocks: They will just not be split all in parallel:

parallel -j30 -a sourcefile.txt --pipepart --block 1M 'mkdir -p prog{#};cat >prog{#}/myfile.txt'

Here we split into blocks around 1 MB with 30 jobs in parallel.


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