Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

How would one make multiple attempts using LWP::UserAgent? I have the following snipped of code: 
$req = HTTP::Request->new(GET => $reqstr);
$req->authorization_basic('username', 'password');
$res = $ua->request($req);$req = HTTP::Request->new(GET => $reqstr);
$req->authorization_basic('username', 'password');
$res = $ua->request($req);

my $title = $ua->request($req)->header('Title');

if (($res->is_success) && ($title ne 'Empty result')) {
    open(OUT,"> $outfile") || die "Could not open $outfile for writing
+: $!\n";
    print OUT  $ua->request($req)->content;
    close OUT;
    exit;
    
## Do not output if there were empty results
} elsif ($res->status_line eq '200 OK') {
    print STDOUT "There were empty results\n";
    #$attempts++;

## Some other error
} else {
    print STDOUT "Error: " . $res->status_line . "\n";
    $attempts++;
    sleep 10;
}

my $title = $ua->request($req)->header('Title');

while ($attempts < 4) {
if (($res->is_success) && ($title ne 'Empty result')) {
    ## Open file handle for output file
    open(OUT,"> $outfile") || die "Could not open $outfile for writing
+: $!\n";
    print OUT  $res;
    close OUT;
    exit;
} elsif ($res->status_line eq '200 OK') {
    print STDOUT "There were empty results\n";
} else {
    print STDOUT "Error: " . $res->status_line . "\n";
}

[download]
My problem lies where I would want the loop to repeat if it's the third case (when it's equivalent to $res->is_error).

Replies are listed 'Best First'.
Re: Looping LWP::UserAgent
by ikegami (Patriarch) on Jun 07, 2005 at 00:46 UTC 
    use strict;
use warnings;

my $tries = 4;
my $sleep = 10;

my $req = HTTP::Request->new(GET => $reqstr);
$req->authorization_basic('username', 'password');

my $res;

my $attempts;
my $success;

for (;;) {
   ++$attempts;
   $res = $ua->request($req);

   if ($res->is_success) {
      my $title = $res->Header('title');

      if ($title ne 'Empty result') {
         $success = 1;
         last;
      }

#else { print("Error: Empty results\n"); }
   }

#else { print "HTTP Error: " . $res->status_line . "\n"; }

   last if $attempts >= $tries;

   # Sleep 10 seconds and try again.
#print("Trying again in $sleep seconds...\n");
   sleep($sleep);
}

die("Unable to download data after $tries tries.\n");
   unless $success;

open(my $out_fh, '>', $outfile)
or die("Could not open $outfile for writing: $!\n");

print $out_fh $req->content;

    [download]

    In your original code, you called $ua->request($req) 4 times before the while. That means that before you even started looping, you were requesting the page 4 times!!

[reply]
[d/l]
[select]
Re: Looping LWP::UserAgent
by tchatzi (Acolyte) on Jun 07, 2005 at 09:26 UTC
    I guess this is what you want 
    use strict;

my $attempts;
my $outfile = "my_file.foo";

my $req = HTTP::Request->new(GET => $reqstr);
$req->authorization_basic('username', 'password');
my $res = $ua->request($req);

my $title = $res->header('Title');

while ($attempts ne 4){
  if (($res->is_success) and ($title ne "")) {
    open(OUT,"> $outfile") or 
      die "Could not open $outfile for writing: $!\n";
    print OUT  $res->content;
    close OUT;
    exit 0;
    
  ## Do not output if there were empty results
  } elsif ($res->status_line eq '200 OK') {
    print "There were empty results\n";
    exit 0;

  ## Some other error
  } else {
    print "Error: " . $res->status_line . "\n";
    print "Will try again in 10 seconds\n";
    sleep 10;
    $attempts++;
  }
}

    [download]


    ``The wise man doesn't give the right answers, he poses the right questions.'' TIMTOWTDI
[reply]
[d/l]

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