UNIX for Beginners Questions & Answers

#!/bin/ksh
for file in [A-Z][A-Z][A-Z][0-9][0-9][0-9][0-9]0[01][0-9]
do	m=${file#????????}
	y=${file#???}
	y=${y%???}
	jd1=$(printf '%(%j)T' "$m/01/$y")
	printf '%s,%s\n' "$file" "$jd1"
done | awk -F ' *, *' '
FNR == NR {
	jdb[ARGV[ARGC++] = $1] = $2 - 1
	next
}
FNR == 1 {
	nofny = substr(FILENAME, 1, 7) ".txt"
	if(ofny && ofny != nofny)
		close(ofny)
	ofny = nofny
	if(ofnm)
		close(ofnm)
	ofnm = FILENAME ".txt"
	gsub(/,/, " ")
	print > ofnm
	print > ofny
	next
}
FNR == 2 {
	gsub(/,/, " ")
	print > ofnm
	print > ofny
	next
}
FNR == 3 {
	printf("Julian  %s  %s\n", $2, $9) > ofnm
	printf("Julian  %s  %s\n", $2, $9) > ofny
	fmt = sprintf("   %%03d  %%4.4s  %%%d.%ds\n", length($9), length($9))
	next
}
{	printf(fmt, $1 + jdb[FILENAME], $2, $9 ? $9 : "-") > ofnm
	printf(fmt, $1 + jdb[FILENAME], $2, $9 ? $9 : "-") > ofny
}' -

   335  1851           8.3
   335  1951           8.3
   335  2051           8.3
   335  2151           8.9
   335  2251           9.4
   335  2351           9.4
   305                   -
Month:  12/2004
Station Name:  "CENTRAL PARK" Call Sign:  NYC
Julian  Time  Dry Bulb Cel
   336  0051           8.9
   336  0151           9.4
   336  0251          10.0
   336  0351           9.4

NF == 0 {
	next
}

FNR == NR {