Linux Swap Space Mini-HOWTO

11. The msinfo.sh script

This shell script analyses the boot sector of the given partition and displays some information along with the "Total Special Sectors" in a message box. It assumes that the filesystem on the given partition is a FAT16. If not, it will print an error message and exit. Invoke it as

 
# msinfo <partition name> 
 

To run this script, you will need the "dialog" program that displays dialog boxes. You can get it from here.

#!/bin/sh 
# 
# msinfo.sh           This shell script displays the boot sector of the 
#                     given partition.
# 
# Author:             Rahul U. Joshi 
# 
# Modifications       Removed the use of expr and replaced it by the let 
#                     command. 
# 
# ------------------------------------------------------------------------
# This program is a free software, you can redistribute it and/or modify
# it under the eterms of the GNU General Public Liscence as published by
# the Free Software Foundation; either version 2 or (at your option) any
# later version.
#
# This program is being distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY without even the implied warranty of
# MERCHANTIBILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
# Public Liscence for more details.
# -------------------------------------------------------------------------
 
 
# check for command line arguments 
if [ $# -ne 1 ]; then 
   echo "Usage: msinfo <partition name>" 
   exit 1 
fi 
 
# check whether the input name is a block device 
if [ ! -b $1 ]; then 
   echo "msinfo: $1 is not a block device" 
   exit 1 
fi 
 
# create two temporary files for use 
TMPFILE=`mktemp -q /tmp/$0.XXXXXX` 
if [ $? -ne 0 ]; then 
    echo "msinfo: Can't create temp file, exiting..." 
    exit 1 
fi 
 
TXTFILE=`mktemp -q /tmp/$0.XXXXXX` 
if [ $? -ne 0 ]; then 
   echo "msinfo: Can't create temp file, exiting..." 
   rm -f $TMPFILE 
   exit 1 
fi 
 
backtitle="`printf "%78s" "msinfo, Information about FAT16 filesystem -- Rahul Joshi"`" 
 
dialog --title "Boot sector of $1" --backtitle "$back_title" \ 
       --infobox "\nAnalysing boot sector for $1\nPlease wait..."  14 60 
 
# truncate TXTFILE to zero length 
echo > $TXTFILE 
 
# get Formatting DOS version 
dd 2>/dev/null if=$1  bs=1 count=8 skip=3 | dd 2>/dev/null of=$TMPFILE 
printf >>$TXTFILE "%30s : %s\n" "Formatting DOS version" "`cat $TMPFILE`" 
 
 
# get file system 
dd 2>/dev/null if=$1  bs=1 count=8 skip=54 | dd 2>/dev/null of=$TMPFILE 
printf >>$TXTFILE "%30s : %s\n" "Filesystem" "`cat $TMPFILE`" 
 
# check if filesystem in a FAT16 
if [ "`cat $TMPFILE`" != "FAT16   " ]; then 
  dialog --title "Boot sector of $1" --backtitle "$back_title" \
         --infobox  "\nCan't find a FAT16 filesystem on $1"  14 60 
  exit 2 
fi 
 
# get volume label in boot sector 
dd 2>/dev/null if=$1  bs=1 count=11 skip=43 | dd 2>/dev/null of=$TMPFILE 
printf >>$TXTFILE "%30s : %s\n" "Volume label in boot sector" "`cat $TMPFILE`" 
  
 
# get Sector size 
dd 2>/dev/null if=$1  bs=1 count=2 skip=11| od -An -tdS | dd 2>/dev/null of=$TMPFILE 
printf >>$TXTFILE "%30s : %d\n" "Sector size" `cat $TMPFILE` 
sector_size=`cat $TMPFILE` 
 
 
# get Reserved sectors 
dd 2>/dev/null if=$1  bs=1 count=2 skip=14| od -An -tdS | dd 2>/dev/null of=$TMPFILE 
printf >>$TXTFILE "%30s : %d\n" " Reserved sectors" `cat $TMPFILE` 
reserved_sectors=`cat $TMPFILE` 
 
 
# get FAT sectors 
dd 2>/dev/null if=$1  bs=1 count=1 skip=16| od -An -tdS | dd 2>/dev/null of=$TMPFILE 
fat_count=`cat $TMPFILE` 
 
dd 2>/dev/null if=$1  bs=1 count=2 skip=22| od -An -tdS | dd 2>/dev/null of=$TMPFILE 
sectors_per_fat=`cat $TMPFILE` 
 
# calculate the no of sectors allocated for FAT's 
let fat_sectors=fat_count*sectors_per_fat 
 
printf >>$TXTFILE "%30s : %u (%u x %u) \n" "FAT sectors" "$fat_sectors" \
        "$fat_count" "$sectors_per_fat" 
 
 
# get root directory sectors 
dd 2>/dev/null if=$1  bs=1 count=2 skip=17| od -An -tdS | dd 2>/dev/null of=$TMPFILE 
root_sectors=`cat $TMPFILE` 
 
# calculate the no of sectors allocated for root directory 
let root_sectors=root_sectors*32/sector_size 
 
printf >>$TXTFILE "%30s : %u\n" "Root directory sectors" "$root_sectors" 
 
 
# get Total special sectors 
let total=reserved_sectors+fat_sectors+root_sectors 
printf >>$TXTFILE "%30s : %u\n" "Total special sectors" "$total" 
 
 
# display the information
dialog --title "Boot sector of $1"  --backtitle "$back_title"  --msgbox "`cat $TXTFILE`" 14 60 
  
# delete temporary files 
rm -f $TMPFILE 
rm -f $TXTFILE 
 
# end of msinfo.sh