Shell Programming and Scripting

awk -F'[.]' '
NR == 1 {
	t = substr($1,5)
	a = 0
}
{	b = substr($1, 3, 2)
	for(i = a; i < b + 0; i++)
		printf("%02d%d\n", i, t)
	a = b + 1
}
END {	for(i = a; i <= 23; i++)
		printf("%02d%d\n", i, t)
}' file

awk -F'[.]' '
FNR == 1 {
	t = substr($1, 5)
}
{	h[substr($1, 3, 2)]
}
END {	for(i = 0; i < 24; i++)
		if(!((hour = sprintf("%02d", i)) in h))
			print hour t
}' file

df01231587.dat
df03231587.dat
df04231587.dat
df06231587.dat 
df07231587.dat 
df08231587.dat 
df09231587.dat 
df10231587.dat 
df11231587.dat 
df12231587.dat 
df13231587.dat 
df14231587.dat 
df16231587.dat
df17231587.dat 
df18231587.dat 
df19231587.dat 
df22231587.dat

00231587
02231587
05231587
15231587
20231587
21231587
23231587

m_ch=` awk -F'[.]' '
  FNR == 1 {
  t = substr($1, 5)
  }
  {       h[substr($1, 3, 2)]
  }
  END {   for(i = 0; i < 24; i++)
  if(!((hour = sprintf("%02d",i "\c")) in h))
  print hour t
  }' file`

echo "$m_ch \c" >> files.txt

awk -F'[.]' '
FNR == 1 {
	t = substr($1, 5)
}
{	h[substr($1, 3, 2)]
}
END {	for(i = 0; i < 24; i++)
		if(!((hour = sprintf("%02d", i)) in h))
			out = (out != "" ? out "," : "") hour t
	print out
}' file >> files.txt

00231587,02231587,05231587,15231587,20231587,21231587,23231587

tr -d '\r' < file > newfile

if [ -f /path/to/file ]; then
  process file
fi