#!/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
}

setglobal COLUMNS = $[tput cols]

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

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

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

setglobal i = '0'
while true {
    progress $shExpr('$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
    setglobal status = $[echo $(PIPESTATUS[@])]
    setglobal dd_status = $[echo $status | cut -f1 -d ' ]
    setglobal 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"; }
    setglobal i = $shExpr('$i+1')
}
echo