[ILUG] regex newbie question

[Hanafin, Jenny]

Hi guys,

I'm trying to come to grips with grep and regular expressions and while I'm making progress, I've come up with some things that puzzle me. Can someone explain to me why grep is returning the following, given the regex I'm using:

[131] ls /data/gps/TEMP 
BELF160z.08o  BELF.apr      dwnld.lst     hers1600.08d  itrf05_eura.apr  lfile.VLNT  MACE160z.08n  MACE160z.08o  MACE208o.08n  MACE208o.08o  MACE213h.08n  MACE213h.08o  mace.lst
VLNT160z.08n  VLNT160z.08o  VLNT213l.08n  VLNT213l.08o  VLNT.apr         vlnt.lst
[132] ls /data/gps/TEMP | grep '^[[:alpha:]]\{4\}[0-9]\{3\}[a-x]\.[0-9]\{2\}[o|n]$'
[133] ls /data/gps/TEMP | grep '^[[:alpha:]]\{4\}[0-9]\{3\}[a-x]\.[0-9]\{2\}[o|n]'
MACE213h.08n  MACE213h.08o  mace.lst      VLNT160z.08n  VLNT160z.08o
VLNT213l.08n  VLNT213l.08o  VLNT.apr      vlnt.lst

What I want is an expression that only returns filenames with a specific format: 4 alphabetic characters, followed by 3 numeric, 1 alphabetic (a-x only), a period, 2 numeric characters and an "o" or an "n" at the end. This is what I think line [132] should return, and I don't understand why the first expression doesn't match any of the filenames. I also don't understand why filenames like 'vlnt.lst' are matched following the command in line [133].

The problem seems to be with the [0-9] and I've tried using [[:digit:]] and [\d] instead but neither of those give me the answers I expect either! 

Any help appreciated, expecially at 4:30 on a Friday ;-)

Thanks,

Jenny