Bash - script to encrypt pdf files using pdfencrypt

Question

I wrote a small script to get around the issue when using pdfencrypt on the command line the password is always echoed as well as being saved to the 'history'.

#!/bin/bash

 export LC_ALL=de_DE.latin1

 while true; do
     echo "please select Pdf input file:"
     read -e -r infile
     if file --mime-type "$infile" | grep -q pdf$; then
         echo
         break
     else
         printf "\nis not a PDF file :-(\n\n"
     fi
 done

 echo "please type in Pdf output filename"
 echo "without extension (.pdf):"
 read -e -r outfile

 if [ -f "${outfile}.pdf" ]; then
     echo
     echo "File allready exists!";
     echo "please enter a new filename, or the same to override: "
     read -e -r outfile
 fi

 echo "please type in Password"
 echo "(only ASCII chracters recommended)"
 read -r -s

 pdfencrypt "$infile" -p "$READ" -o "${outfile}.pdf" \
  && echo "success, ${outfile}.pdf is encrypted :-)" \
  || echo "failed, did you use non ASCII characters for Password?"

exit

I had the problem with following non ASCII-Characters in the password: § ä ö ü etc. When I used any of those for encryption I got the following error:

Encoding::CompatibilityError: incompatible character encodings: UTF-8 and ASCII-8BIT

I solved this by including export LC_ALL=de_DE.latin1 in the script. Though there still are some compatibility problems when using any of those characters, therefore I added a recommendation not to use non ASCII in the password.

(I know that PDF encryption itself is pretty low-level security but I sometimes like to add this level when sending files via e-mail etc...)

Answer 1

Usability

Typing filenames on standard input is extremely annoying. It would be better if the script took the input filename as command line argument. That way users can benefit from path completion in the shell.

Simplify

Instead of this:

 while true; do
     echo "please select Pdf input file:"
     read -e -r infile
     if file --mime-type "$infile" | grep -q pdf$; then
         echo
         break
     else
         printf "\nis not a PDF file :-(\n\n"
     fi
 done

I would eliminate the else statement, and also simplify the echo-ing:

 while true; do
     echo "please select Pdf input file:"
     read -e -r infile
     echo
     file --mime-type "$infile" | grep -q pdf$ && break
     echo "is not a PDF file :-("
     echo
 done

Redundant exit

The exit at the end of the script is redundant, I suggest to remove it.