faster_grep

#!/usr/bin/env bash

# Martin Kersner, m.kersner@gmail.com
# 2016/04/08

# faster_grep $1 $2
# $1 pattern file
# $2 input file

PATTERN_FILE="$1"
INPUT_FILE="$2"

TMP_FILE=$(mktemp /tmp/faster_grep.XXXXXX)
exec 3>"$TMP_FILE"
rm "$TMP_FILE"

cat "$INPUT_FILE" > "$TMP_FILE"

NUM_LINE_INPUT=0
while IFS='' read -r LINE || [[ -n "$LINE" ]]; do
 GREP_OUT=`grep -n "$LINE" "$TMP_FILE"`

 if [ "$GREP_OUT" ]; then
   NUM_LINE_PAT=`grep -o "^[0-9]*" <<< "$GREP_OUT"`
   MATCH=`grep -o "/.*$" <<< "$GREP_OUT"`
   echo "$MATCH"

   NUM_LINE_INPUT=$((NUM_LINE_PAT+NUM_LINE_INPUT))
   tail -n +${NUM_LINE_INPUT} ${INPUT_FILE} > ${TMP_FILE}
 fi
done < "$PATTERN_FILE"