Please keep in mind that this post is about 3 years old.
Technology may have changed in the meantime.

I am an author. And even though the actual books are well-organized, the writing process isn’t always. For a single book I have many mega-bytes of PDFs, ODTs and text files full of notes, drafts, documentation, etc.
So I needed a simple tool to find that one note I once wrote, in that huge pile of data.
Now, if those files were all text-based, I could use grep. But they aren’t. So I wrote a wrapper around grep, that allows me to also search PDFs and OpenDocument files.

This script searches all PDFs, OpenDocument files and text-based files in the current directory for a given term; the search is case-insensitive, and does not recurse into sub-directories.

Example:

$ multigrep 'SSH key'

Here’s the script:

#!/usr/bin/env bash

################################################################################

#                                 multigrep
#                                 door  Rob

# rob@ohreally.nl
################################################################################
# https://www.ohreally.nl

# This script searches all PDF, OpenDocument and text-based files
# in the current directory for the given string.

# For more info, see
# https://www.ohreally.nl/2020/12/11/multigrep/

################################################################################

# Copyright (c) 2020 Rob La Lau 

# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:

# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.

# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.

################################################################################

CAT=`which cat`             || exit 1
FILE=`which file`           || exit 1
GREP=`which grep`           || exit 1
PDF2TXT=`which pdf_to_text` || exit 1
SED=`which sed`             || exit 1
TIDY=`which tidyp`          || exit 1
UNZIP=`which unzip`         || exit 1

pattern=$@

process() {
	while read input; do
		"${GREP}" -i "${pattern}" | "${SED}" -e "s/^ */${file}: /;s/ *$//"
	done
}

for file in *; do
	[ -d "${file}" ] && {
		echo "  Directory : ${file}"
		continue
	}
	mimetype=`"${FILE}" --brief --mime-type "${file}"`
	major=${mimetype%%/*}
	minor=${mimetype##*/}
	case "${major}" in
		application)
			case "${minor}" in
				pdf)
					# PDF
					"${PDF2TXT}" --file "${file}" 2> /dev/null | process
					;;
				vnd.oasis.opendocument.*)
					# OpenDocument (all)
					"${UNZIP}" -p "${file}" | "${TIDY}" -quiet -xml -bare -utf8 2> /dev/null | process
					;;
				*)
					echo "  Unknown file type (${mimetype}) : ${file}"
					;;
			esac
			;;
		text)
			# text/*
			"${CAT}" "${file}" | process
			;;
		*)
			echo "  Unknown file type (${mimetype}) : ${file}"
			;;
	esac
done

This script can also be downloaded from my Github account.