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Diffstat (limited to 'sutils/e2os.sh')
| -rwxr-xr-x | sutils/e2os.sh | 143 |
1 files changed, 143 insertions, 0 deletions
diff --git a/sutils/e2os.sh b/sutils/e2os.sh new file mode 100755 index 00000000..028f076e --- /dev/null +++ b/sutils/e2os.sh @@ -0,0 +1,143 @@ +#!/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=/bin/dd +OD=/bin/od +SED=/bin/sed +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 + +# 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;; + "*[!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;; + $OS_MASIX) OS=masix;; + esac + echo "$OS" +fi |