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#!/bin/sh
# Set/get the `creator_os' field of an ext2fs partition
#
# Copyright (C) 1996 Free Software Foundation, Inc.
#
# Written by Miles Bader <miles@gnu.ai.mit.edu>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2, or (at your option)
# any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
#
DD=${DD-/bin/dd}
OD=${OD-/bin/od}
SED=${SED-/bin/sed}
AWK=${AWK-/bin/gawk}
USAGE="Usage: $0 DEVICE [OS]"
while :; do
case "$1" in
--help|"-?")
echo "$USAGE"
echo "Get or set the creator_os parameter of an ext2fs partition."
echo ""
echo " -?, --help Give this help list"
echo " --usage Give a short usage message"
echo " -V, --version Print program version"
exit 0;;
--usage)
echo "Usage: $0 [-V?] [--help] [--usage] [--version] DEVICE [OS]"
exit 0;;
--version|-V)
echo "e2os 1.0 (`uname -sr`)"; exit 0;;
-*)
echo 1>&2 "$0: unrecognized option \`$1'"
echo 1>&2 "Try \`$0 --help' for more information";
exit 1;;
*)
break;;
esac
done
case "$#" in 1 | 2) ;; # ok
*) echo 1>&2 "$USAGE"
echo 1>&2 "Try \`--help' for more information";
exit 1;;
esac
DEVICE="$1"; shift
OS="$1"
# Superblock fields (format is "BYTE_OFFS SIZE")
SB_MAGIC="56 2"
SB_OS="72 4"
# Ext2fs magic numbers
MAGIC_EXT2=ef53
MAGIC_EXT2_OLD=ef53
# Symbolic names for os types we know about
OS_LINUX=0
OS_HURD=1
OS_MASIX=2
OS_FREEBSD=3
OS_LITES=4
# Superblock
SB=/tmp/,e2os-sb.$$
# We have to store error output in a file so that we can filter it (for all
# unix's stressing of pipelines, /bin/sh sure works hard to prevent you using
# them).
ERRS=/tmp/,e2os-errs.$$
trap "/bin/rm -f $SB $ERRS" 0
# Read the superblock
$DD 2>"$ERRS" if="$DEVICE" of="$SB" bs=1k skip=1 count=1 \
|| { $SED 1>&2 "s;^$DD:;$0:;" "$ERRS"; exit 2; }
# Extract a word of SZ bytes from byte offset POS in the superblock
# Optional arg FMT is what format to use (x = hex, d = decimal)
function sbget
{
local pos="$1" sz="$2" fmt="${3-d}"
pos=$(($pos / $sz))
$DD 2>/dev/null if="$SB" bs="$sz" skip="$pos" count=1 \
| $OD -An -t"$fmt$sz" \
| $SED 's;^[ 0]*\(.\);\1;'
}
# Set a word of SZ bytes at byte offset POS in the superblock to VAL
function sbset
{
local pos="$1" sz="$2" val="$3"
pos=$(($pos / $sz))
echo "$val" \
| $AWK '{ n=$1+0; printf ("%c%c%c%c", n, n/256, n/(2^16), n/(2^24)); }' \
| $DD 2>/dev/null of="$SB" bs="$sz" seek="$pos" count=1 conv=notrunc
}
# Check the magic number
magic="`sbget $SB_MAGIC x`"
case "$magic" in
$MAGIC_EXT2) ;; # ok
$MAGIC_EXT2_OLD) echo "$0: $DEVICE: Old-format ext2 filesystem"; exit 3;;
*) echo "$0: $DEVICE: Not an ext2 filesystem (magic = 0x$magic)"; exit 4;;
esac
if test "$OS"; then
# Set the os field
case "$OS" in
linux) OS=$OS_LINUX;;
hurd) OS=$OS_HURD;;
masix) OS=$OS_MASIX;;
freebsd) OS=$OS_FREEBSD;;
lites) OS=$OS_LITES;;
"*[!0-9]*")
echo 1>&2 "$0: $OS: Unknown ext2 creator_os value"; exit 5;;
esac
# Frob the superlock
sbset $SB_OS "$OS"
# Write the superblock
$DD 2>"$ERRS" if="$SB" of="$DEVICE" bs=1k seek=1 count=1 \
|| { $SED 1>&2 "s;^$DD:;$0:;" "$ERRS"; exit 6; }
else
# Print the os field.
OS="`sbget $SB_OS`"
case "$OS" in
"") exit 2;;
$OS_LINUX) OS=linux;;
$OS_HURD) OS=hurd;;
$OS_MASIX) OS=masix;;
$OS_FREEBSD) OS=freebsd;;
$OS_LITES) OS=lites;;
esac
echo "$OS"
fi
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