#!/bin/bash

# search disk for a string and output commands to dump matching sections

# License: LGPLv2

# Author:

# http://www.pixelbeat.org/

# Notes:

# On my Fedora 8 system members of the "disk" group are

# allowed to read the disk devices, so to do that:

# sudo /usr/sbin/usermod -a -G "disk" $USER

# sudo su - $USER

# Changes:

# V0.1, 20 Apr 2008, Initial release

# V0.3, 29 Sep 2010

# http://github.com/pixelb/scripts/commits/master/scripts/disk_grep

usage() {

echo "Usage: $(basename $0) file|device string" >&2

exit 1

}

COLUMNS=$(tput cols)

#pass % complete

progress() {

DONE=$(( (($COLUMNS-2)*$1)/100 ))

TODO=$(($COLUMNS-2-$DONE))

DONE=$(printf "%${DONE}s" | tr ' ' =)

TODO=$(printf "%${TODO}s" | tr ' ' -)

printf "[$DONE$TODO]\r" > /dev/tty

}

#pass strings to stdout

print() {

CLEAR=$(printf "%${COLUMNS}s")

printf "$CLEAR\r"

echo "$@"

}

[ $# -ne 2 ] && usage

DISK="$1"

STRING="$2"

export LANG=C

# Note we must manage these limits ourselves

# because dd currently does not fail if you seek

# past the end of a file or device. In fact for devices

# it reads the whole device when you do this!

#

# This also allows us to show completion progress

CHUNK_SIZE=$((8*1024*1024))

if [ -b "$DISK" ]; then

SIZE=$(/sbin/blockdev --getsize64 $DISK) || exit $? #reads from disk?

else

SIZE=$(stat --format %s "$DISK") || exit $?

fi

[ $SIZE -eq 0 ] && exit

CHUNKS=$((($SIZE+$CHUNK_SIZE-1)/$CHUNK_SIZE))

i=0

while true; do

progress $(($i*100/$CHUNKS))

[ "$i" -ge "$CHUNKS" ] && break

# use "direct" flag so cache not polluted with read data

dd if=$DISK iflag=direct conv=noerror bs=$CHUNK_SIZE count=1 skip=$i 2>/dev/null |

#we ensure grep reads all data, otherwise dd will get SIGPIPE and exit with 141

grep --binary-files=text -U -F "$STRING" >/dev/null

status=$(echo ${PIPESTATUS[@]})

dd_status=$(echo $status | cut -f1 -d ' ')

re_status=$(echo $status | cut -f2 -d ' ')

[ $dd_status -ne 0 ] && { echo "dd error" >&2; exit $dd_status; }

[ $re_status -eq 0 ] && { print "dd if=$DISK iflag=direct bs=$CHUNK_SIZE count=1 skip=$i > disk_grep.$i"; }

i=$(($i+1))

done

echo