From: Ben Giddings <bg-rubytalk@...>
Date: 2007-10-16T06:38:57+09:00
Subject: Re: pulling a file with today's date

On Monday 15 October 2007, Peter Bailey wrote:
> Hi,
> Can someone please help me to parse a file by its date so that, when I
> ftp to a site, I only pull those files that are dated with today's 
date,
> nothing else? I'm OK with pulling all files over, looking at them on 
my
> side of the fence, and then just discarding those files that aren't
> timestamped with today's date.

When you say "parse a file", do you mean parse the contents of the file, 
or simply select a specific file?  I think you're talking about 
choosing a file based on the filename matching a date, but I'm not 
sure.

The answer really depends on the format of the date.  If it's a nice 
iso8601 format date string (i.e. YYYY-MM-DD) it's a little easier than 
other formats, but none of them is really hard.  Basically all you have 
to do is create a regular expression object that will match the pattern 
you're looking for.  You create the regexp based off a date string that 
comes from today's date

For example, if the file is 2007-10-15-secretdata.zip:

First create a string with the current date formatted however the date 
in the filename is formatted:
date_str = Time.new.strftime("%Y-%m-%d")

Next create a regular expression based on that string:
file_match_regex = Regexp.new("^" + date_str + "-secretdata.zip$")

Finally match the filenames against that regular expression:
irb(main):008:0> file_match_regex.match("2007-10-15-secretdata.zip")
=> #<MatchData:0xb7a3be04>
irb(main):009:0> file_match_regex.match("2007-10-16-secretdata.zip")
=> nil

If you want to do this on the remote files, you'll probably want to use 
Ruby's FTP libraries.  If you want to do it after you transfer the 
files over, you can transfer the file and then check them based on 
whatever matches the regexp.

Ben