#!/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

proc usage {
    echo "Usage: $[basename $0] file|device string" > !2
    exit 1
}

global COLUMNS := $[tput cols]

#pass % complete
proc progress {
    global DONE := $( (($COLUMNS-2)*$1)/100 )
    global TODO := $($COLUMNS-2-$DONE)
    global DONE := $[printf "%$(DONE)s" | tr ' ' =]
    global TODO := $[printf "%$(TODO)s" | tr ' ' -]
    printf "[$DONE$TODO]\r" > /dev/tty
}

#pass strings to stdout
proc print {
    global CLEAR := $[printf "%$(COLUMNS)s]
    printf "$CLEAR\r"
    echo @Argv
}

test $Argc -ne 2 && usage
global DISK := $1
global 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
global CHUNK_SIZE := $(8*1024*1024)
if test -b $DISK {
    global SIZE := $[/sbin/blockdev --getsize64 $DISK] || exit $Status #reads from disk?
} else {
    global SIZE := $[stat --format %s $DISK] || exit $Status
}
test $SIZE -eq 0 && exit
global CHUNKS := $(($SIZE+$CHUNK_SIZE-1)/$CHUNK_SIZE)

global i := '0'
while true {
    progress $($i*100/$CHUNKS)
    test $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
    global status := $[echo $(PIPESTATUS[@])]
    global dd_status := $[echo $status | cut -f1 -d ' ]
    global re_status := $[echo $status | cut -f2 -d ' ]
    test $dd_status -ne 0 && do { echo "dd error" > !2; exit $dd_status; }
    test $re_status -eq 0 && do { print "dd if=$DISK iflag=direct bs=$CHUNK_SIZE count=1 skip=$i > disk_grep.$i"; }
    global i := $($i+1)
}
echo
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