On 22Jul2006 12:54, Michael Sullivan <[EMAIL PROTECTED]> wrote:
| I'm trying to create a mail filter script in perl. The user will send
| mail to the script and the script will hold the mail until it receives
| further orders from the script. Each individual email needs to be
| stored in its own file while waiting to be processed. I want a random
| code for the filename to be used for each individual email. I was
| thinking something like this:
|
| date +%N | md5sum
|
| However, while I can call this command using exec(), how do I use the
| output in my script?
Like this:
$code = `date +%N | md5sum`; # collect output of shell command
chomp($code); # trim the trailing newline
However, a few remarks:
- %N is nanoseconds, but on most systems it is not so precise.
Try "%s.%N", or even "%s.%N.$$" (note the double quotes - we're
relying on the shell replacing $$ with the process id here).
- MD5 is a one-way hash. So the output of MD5sum is inherently _smaller_
than the possible inputs. So you're better off just using the output
of the date command unless there is some consideration you have not
mentioned.
- Running a shell command to do this is pretty slow. In fact, REALLY
REALLY slow. You are only getting the current time and (needlessly)
performing a hash computation on it. Compared to the work involved in
forking processes, firing up new commands (loading from disc if
not cached, linking shared libraries, rewriting process address spaces)
it's a tiny amount of work, grossly smaller that the new process
overhead.
It's only worth doing that work if it's hard to do the job inside
perl.
Consider this:
$code = time+".$$"; # time in seconds plus process id
It should be sufficiently unique, and it's quite fast.
Cheers,
--
Cameron Simpson <[EMAIL PROTECTED]> DoD#743
http://www.cskk.ezoshosting.com/cs/
It's there as a sop to former Ada programmers. :-)
- Larry Wall regarding 10_000_000 in <[EMAIL PROTECTED]>
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