Shell Programming and Scripting

#!/bin/ksh
# Usage: splittype [ EBCDICfile.ebc ]
# The splittype utility shall extract records from the given input file
# (default data.ebc if no operand is given) into files named "Type"xx".ebc"
# (where xx is the record type identified by the 1st two bytes of each 422
# EBCDIC-encoded byte record in the input file).  The input file pathname is
# assumed to end with the extenions ".ebc".  If it doesn't, the results are
# unspecified.  Records found in the input file will be appended to the
# corresponding output files in the current directory.

# If an ASCII version of the input file does not exist in the current directory
# with the same basename as the input file and with the same size as the input
# file with the extension ".ascii", it will be created (or, if it exists with a
# different size, overwritten) before processing starts.
IAm=${0##*/}
ec=0			# Final exit code.
ifEBCDICname=${1:-data.ebc}
ifASCIIname=${ifEBCDICname##*/}
ifASCIIname="${ifASCIIname%.ebc}.ascii"
ofname_prefix="Type"	# Output filenames will be...
ofname_suffix=".ebc"	#	"$ofname_prefix$type$ofname_suffix"

fixlen=522		# Fixed length of records in input file.
spot=0			# # of bytes processed so far from input file.

# Verify that the input file exists...
if [ -f "$ifEBCDICname" ]
then	read junk junk junk junk fsize junk <<-EOF
		$(ls -l "$ifEBCDICname")
	EOF
else	printf '%s: ERROR: File "%s" not found.\n' "$IAm" "$ifEBCDICname" >&2
	exit 1
fi
printf '%s: NOTE: Processing input file "%s" (%d bytes)\n' "$IAm" \
    "$ifEBCDICname" "$fsize" >&2

# Look for ASCII version of input file and create it if needed...
if [ ! -f "$ifASCIIname" ] ||
   [ "$(ls -l "$ifASCIIname" | (read x x x x Afsize x; echo "$Afsize"))" -ne \
	$fsize ]
then	printf '%s: NOTE: Creating ASCII version of "%s"\n' "$IAm" \
	    "$ifEBCDICname" >&2
	if ! dd if="$ifEBCDICname" of="$ifASCIIname" conv=ascii
	then	printf '%s: ERROR: Could not create ASCII file "%s".\n' "$IAm" \
		    "$ifASCIIname" >&2
		exit 2
	fi
fi
while [ $spot -lt $fsize ]
do	type="$(dd if="$ifASCIIname" bs=1 skip=$spot count=2 2>/dev/null)"
	case "$type" in
	(01)	typelen=152;;
	(02)	typelen=172;;
	(*)	printf '%s: Unknown file type ("%s") found at offset %d\n' \
		    "$IAm" "$type" $spot >&2
		spot=$((spot + fixlen))
		ec=3
		continue;;
	esac
	dd if="$ifEBCDICname" bs=1 skip=$spot count=$typelen >> \
	    "$ofname_prefix$type$ofname_suffix" 2>/dev/null
	spot=$((spot + fixlen))
done
exit $ec