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-rwxr-xr-xsutils/e2os.sh143
1 files changed, 143 insertions, 0 deletions
diff --git a/sutils/e2os.sh b/sutils/e2os.sh
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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=/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