This atrocious shell script prints the first 1/nth (half, third, etc) part of a file

splitter.sh

#!/bin/sh
#get the command line arguments
input_file=$1
divisor=$2
#run wc on the file in argv[1]
size=`wc -l $input_file`
#split the return on whitespace - first word is now in 
set $size
#get the intiger division of wc/divisor
part=$(($1/$divisor))
#print the first part (wc/divisor)
head -$part $input_file

Example run:
sh split.sh file n
N is the divisor