Interesting script from @pmocek for renaming certain .PDFs

Jstor PDF renaming

#!/bin/bash

# See discussion at <http://twitter.theinfo.org/95208900873302016>

# Search a directory for files with names ending in ".pdf".
# For each of those:
#   If a file with similar name, ending in ".txt" instead of ".pdf" exists:
#     If the text file contains a line beginning with "T1":
#       Read the rest of the line to find a title
#       Write the PDF's metadata to a temporary file
#       If the metadata already includes a title:
#         Replace title with the one found in the text file
#       Otherwise:
#         Add title found in text file
#       Update the PDF with values from the temp file, leaving original renamed like "*.pdf.orig"

search_dir="/tmp"
find "$search_dir" -name '*.pdf' | while read pdf_file; do
    text_file="${pdf_file/%.pdf/.txt}"
    if [ -f "$text_file" ]; then
        # Corresponding text file exists
        new_title="$(grep '^T1' "$text_file" | sed -e's/^T1 \+- \+\(.*\)/\1/')"
        if [ -n "$new_title" ]; then
            # Extracted a title from external metadata
            old_metadata=$( mktemp )
            new_metadata=$( mktemp )
            pdftk "$pdf_file" dump_data output $old_metadata
            if grep -q '^InfoKey: Title' $old_metadata ; then
                # Replace existing title in PDF metadata with new title
                cat $old_metadata | while read -r key value ; do
                    case "$key" in
                        "InfoKey:" )
                            infokey="$value"
                            ;;
                        "InfoValue:" )
                            if [ "$infokey" == "Title" ]; then
                                value="$new_title"
                                unset infokey
                            fi
                            ;;
                     esac
                     echo "$key" "$value" >> $new_metadata
                     done
            else
                # Add new title to PDF metadata
                cp $old_metadata $new_metadata
                echo "InfoKey: Title"        >> $new_metadata
                echo "InfoValue: $new_title" >> $new_metadata
            fi
            #diff -u $old_metadata $new_metadata
            pdftk "$pdf_file" update_info "$new_metadata" output "${pdf_file}.new"
            mv "$pdf_file" "${pdf_file}.orig"
            mv "${pdf_file}.new" "$pdf_file"
            rm $old_metadata
            rm $new_metadata
        else
            echo "No T1 line in $text_file" >&2
        fi
    else
        echo "No corresponding metadata file for $pdf_file" >&2
    fi
done