Posted on 1999-01-18
Last Modified: 2010-03-05
I use Unix

Is there a command in perl where you can say something like:

In 30 min execute {
(stuff to execute)

And that it would do it, even if the user's browser is no longer open?  Thanks
Question by:jknickelbein
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Expert Comment

ID: 1210195
  man at
  perldoc -f localtime

I've got to go now, but I'll post some code tomorrow (or someone else will do it before...).


Expert Comment

ID: 1210196
Unless you had Perl spawn another process at runtime,
the only way you'd get it going is to system an "at" command.
A keepalive connection would (in theory) work but it's doubtful
they're going to keep a page open for 30 mins...


Author Comment

ID: 1210197
Using the at command is kinda what martinag already said.... if you can explain how to use it, I'll award to him the points.
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Author Comment

ID: 1210198
Really, all I need done, is that 30 minutes after my user logs into my script, I want to delete a certain file, thus expiring the session.

Expert Comment

ID: 1210199
# Random file name
$file = "exec" . time . "pid$$.ex"; # millisecs since 1970 and pid should be enough random

# Write file that should be "executed"
open (FILE, ">$file") or die "can't open $file for output: $!";
print FILE "rm ..."; # The command
close FILE;

# Calculate time
@time = localtime;
$h = $time[2];
$m = $time[1] + 30;
if ($m > 59) {
  $h = 0 if $h++ == 24;
  $m -= 60;

# Set timer
system("at -f $file " . sprintf("%2d:%2d", $h, $m));


Accepted Solution

Cov earned 20 total points
ID: 1210200

Another approach you could use would be to simply keep a process excecuting on the server which makes sure everything is cleared out if it is 30 minutes old... just clearing the directory every 30 minutes would work, but then some people would have shorter "login" times than others.

Try something like this:
Build a perl script which will check the directory every minute for aged files and delete them.  When it launched, have the script record its PID (process id) to a file.

No, have your other perl scripts which users interact with have a function that just occasionally checks that data file for the pid and checks to see if it is still alive.  If it isnt, have it reexecute ... that is your safe guard...

And voila:)  Every thing will run fine...
i still think it would be simpler just to have you login script clear out old entries... it would not take much process time...

Author Comment

ID: 1210201
Ok... thanks guys!

Cov - as long as it should take to long (process time) to clear out all over 30min. entries, that's probably what I'll do.

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