Subjectively

#!/bin/bash
#===============================================================================
#
#          FILE:  chunkfile.sh
# 
#         USAGE:  ./chunkfile.sh 
# 
#   DESCRIPTION:  split a text file by lines
# 
#       OPTIONS:  ---
#  REQUIREMENTS:  ---
#          BUGS:  ---
#         NOTES:  ---
#        AUTHOR:  Kirk Roybal (DBA), kroybal@kalkomey.com
#       COMPANY:  Kalkomey
#       VERSION:  1.0
#       CREATED:  12/30/2011 09:45:42 AM CST
#      REVISION:  ---
#===============================================================================
 
 
ScriptVersion="1.0"
 
#===  FUNCTION  ================================================================
#         NAME:  usage
#  DESCRIPTION:  Display usage information.
#===============================================================================
function usage ()
{
	cat <<- EOT
 
  Usage :  ${0##/*/} [options] [--] 
 
  Options: 
  -c|chunks #   Number of chunks
  -d|debug      Display bash debugging info
  -e|ext  exten Output file extension
  -f|file name  File to chunk
  -h|help       Display this message
  -j|just pad   Padding zeros for output files
  -l|log        Display logging information
  -p|prefix pre Prefix of new file names
  -v|version    Display script version
 
  Note:  using multiple logging options increases the log level
  (i.e.) ${0##/*/} -lll -f input.txt -c 3 -j 2 -p output
  Log level 3.
 
  Output:
  output_01.txt
  output_02.txt
  output_03.txt
 
 
	EOT
}    # ----------  end of function usage  ----------
 
#-----------------------------------------------------------------------
#  Handle command line arguments
#-----------------------------------------------------------------------
 
padding=2
 
while getopts ":c:de:f:hj:lp:v" opt
do
  case $opt in
 
    c|chunks   )  chunks=$OPTARG;;
 
    d|debug    )  set -x;;
 
    e|ext      )  ext=".$OPTARG";;
 
    f|file     )  filename=$OPTARG
                  ext=".${filename#*.}"
                  [[ -z $prefix ]] && prefix="$(basename ${filename} $ext)_"
                  ;;
 
    h|help     )  usage; exit 0   ;;
 
    j|just     ) padding=$OPTARG;;
 
    l|log      ) (( logging++ ));;
 
    p|prefix   ) prefix=$OPTARG;;
 
    v|version  )  echo "$0 -- Version $ScriptVersion"; exit 0   ;;
 
    \? )  echo -e "\n  Option does not exist : $OPTARG\n"
          usage; exit 1   ;;
 
  esac    # --- end of case ---
done
shift $(($OPTIND-1))
 
[[ -z $filename ]] && [[ -z $prefix ]] && {
	cat <<- EOT
 
  You must specify a filename or a prefix for output.
  (i.e.) ${0##/*/} -f input.txt -c 3 -j 2 
  or
  (i.e.) cat input.txt | ${0##/*/} -c 3 -j 2 -p output
 
	EOT
  usage
  exit 1
}
 
#take input from stdin
[[ -z $filename ]] && filename="-"
 
[[ -z $chunks ]] && {
  usage
  exit 1
}
 
guts=$(tempfile)
cat "$filename" > "$guts"
 
filesize=$(cat "$guts" | wc -l)
chunksize=$((filesize/chunks))
[[ $((filesize%chunks)) -gt 0 ]] && (( chunksize++))
 
for ((i=0;i<$chunks;i++))
do
  dest="${prefix}$(printf "%0${padding}i" $(($i + 1)))$ext"
  cat "$guts" | tail -n +$((($i*$chunksize)+1)) | 
    head -n $chunksize > "$dest"
done
 
[[ -f "$guts" ]] && rm "$guts"