#!/bin/sh
#
# This command prints a track from a CKD DASD image file.
# It uses the GNU Octal Dump (od) command to firstly obtain
# the device geometry from the CKD header, and secondly to
# print the track in hexadecimal format.
#
filename=$1
cyl=$2
head=$3

if [ -z $filename ]; then
    echo "Usage: dasdlist filename [cyl head]"
    exit 1
fi

if [ ! -e $filename ]; then
    echo "File $filename does not exist"
    exit 1
fi

#
# Check the first 8 bytes of the header for valid CKD DASD image file
#
ckdid=`hexdump -n 8 -e '"%_p"' $filename`
if [ $ckdid != "CKD_P370" ]; then
    echo "File $filename is not a CKD DASD image file"
    exit 2
fi

#
# The next 8 bytes contain the tracks/cyl and track length constants
#
heads=`od -An -tu4 -j 8 -N 4 $filename`
trklen=`od -An -tu4 -j 12 -N 4 $filename`

echo "$filename $(($heads)) trks/cyl, $(($trklen)) bytes/trk"

#
# If cylinder number is not given then exit
#
if [ -z $cyl ] || [ -z $head ]; then
    echo "To dump a track specify dasdlist $filename cyl head"
    exit 0
fi

#
# Calculate the offset to the requested cylinder and track
#
offset=$((512+(($cyl*$heads)+$head)*$trklen))
num=$(($trklen))

#
# Dump the requested track
#
echo "$filename Cyl $(($cyl)) Head $(($head))"
echo "od -Ax -tx1 -j $offset -N $num $filename"
od -Ax -tx1 -j $offset -N $num $filename