merge-scanned-docs

#!/bin/bash

# prints help text 
# exits 0
help() {
  echo "merges double printed documents scanned twice";
  echo "usage: merge-scanned-docs <docpath>";
  echo "assumes two PDFs named <docpath>_odd.pdf and <docpath>_even.pdf";
  echo "assumes that <docpath>_even.pdf is in reverse order";
  echo "generates a new PDF named <docpath>.pdf";
  exit 0;
}

# checks if a file or directory exists
# param 1: the file to check
# returns 0: if the file or directory doesn't exist
# exits 1: if the file or directory exists
checkF() {
  if [ -f "$1" ]; then
    echo "file '$1' already exists. aborting".
    exit 1;
  fi
  return 0;
}

# checks reada access of a file
# param 1: the file to check
# returns 0: if the file exist
# exits 1: if the file either doesn't exist or no read permission are granted 
checkR() {
  if [ ! -e "$1" ]; then
    echo "file '$1' not found. aborting.";
    exit 1;
  fi
  if [ ! -r "$1" ]; then
    echo "no read permission for file '$1' granted. aborting.";
    exit 1;
  fi
  return 0;
}

# start
if [ -z "$1" ]; then
  help;
fi

# build 3 filenames
inA="$1_odd.pdf";
inB="$1_even.pdf";
out="$1.pdf";

# check files
checkR $inA;
checkR $inB;
checkF $out;

# merge files
pdftk A="$inA" B="$inB" shuffle A Bend-1 output "$out";