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

Hello Wise Monks...

I have the following code running as CGI. It starts to run and returns an empty PDF file to the browser and writes an error message to the error_log.

Do you have any wisdom on how to solve this?

linux: Linux version 2.6.35.6-48.fc14.i686.PAE (...) (gcc version 4.5.
+1 20100924 (Red Hat 4.5.1-4) (GCC) ) #1 SMP Fri Oct 22 15:27:53 UTC 2
+010

wkhtmltopdf: wkhtmltopdf 0.10.0 rc2

perl: This is perl 5, version 12, subversion 2 (v5.12.2) built for i38
+6-linux-thread-multi

[download]

Thank You in Advance. ~Donavon

perl CODE:

#!/usr/bin/perl
#### takes string containing HTML and outputs PDF to browser to downlo
+ad
#### (otherwise would output to STDOUT)

print "Content-Disposition: attachment; filename='testPDF.pdf'\n";
print "Content-type: application/octet-stream\n\n";

my $htmlToPrint = "<html>a bunch of html</html>";

### open a filehandle and pipe it to wkhtmltopdf
### *the arguments "- -" tell wkhtmltopdf to get
###  input from STDIN and send output to STDOUT*
open(my $makePDF, "|-", "/usr/local/bin/wkhtmltopdf", "-", "-") || die
+("$!");
print $makePDF $htmlToPrint;  ## sends my HTML to wkhtmltopdf which st
+reams immediately to STDOUT

[download]

error_log message:

Loading pages (1/6)
QPainter::begin(): Returned false============================] 100%
Error: Unable to write to destination

[download]

Replies are listed 'Best First'.
Re: perl wkhtmltopdf Error: Unable to write to destination
by RichardK (Parson) on May 07, 2014 at 16:25 UTC

    '|-' means open a command and pipe data to it, & the help for open says :-

    You are not allowed to "open" to a command that pipes both in and out,
+ but see
       IPC::Open2, IPC::Open3,...

    [download]

    So it's no great surprise that it doesn't work.

[reply]
[d/l]

      Thank you for your response.

      I will try it with IPC::Open3.

      I'm trying to create a simple example for IPC::Open3. Should I create a separate post relating to getting Open3 to work?

      Below is code I am trying and here is the output I get:

      OUTPUT: 
      err-> /bin/ls: write error: Bad file descriptor retval-> 512

      [download]
      CODE: 
      #!/usr/bin/perl
use warnings;
use strict;
use IPC::Open3;

print "Content-type: text/html\n\n";

print ' <!DOCTYPE HTML>
        <html lang="en">
        <head>
          <title>IPC::Open3 Example</title>
        </head>
        <body>';

        
my $cmd = '/bin/ls -la';

my $pid = open3(\*WRITER, \*READER, \*ERROR, $cmd);

while( my $output = <READER> ) {
  print "output-> $output\n";
}

while(my $errout = <ERROR> ) {
  print "err-> $errout\n";
}

waitpid($pid, 0 ) or die "$!\n";
my $retval =  $?;
print "retval-> $retval\n";

print " </body>
        </html>";

      [download]
[reply]
[d/l]
[select]

        Here is the final working solution I came up with. If there is anything I missed please let me know. I don't know if I am using "gensym()" correctly. The main thing that was an issue was rights on the server side.

        #!/usr/bin/perl
use warnings;
use strict;
use IPC::Open3;
use Symbol;

my $cmd = '/usr/local/bin/wkhtmltopdf - -';

my $err = gensym(); 
my $in  = gensym();
my $out = gensym();

my $pdf = '';

my $pid = open3($in, $out, $err, $cmd)  or die "could not run cmd : $c
+md : $!\n";

my $string = '<html><head></head><body>Hello World!!!<br /><br /><br /
+>
IMG: <img id="image" src="data:image/gif;base64,R0lGODlhFwAPAKEAAP///w
+AAAMzMzLi3tywAAAAAFwAPAAACQIyPqQjtD98RIVpJ66g3hgEYDdVhjThyXSA4aLq2rgp
+78hxlyY0/ICAIBhu/HrEEKIZUyk4R1Sz9RFEkaIHNFgAAOw==" />
</body></html>';

print $in $string;
close($in);

while( <$out> ) {
  $pdf .= $_
}

# for trouble shooting
while( <$err> ) {
  # print "err-> $_<br />\n";
}

# for trouble shooting
waitpid($pid, 0 ) or die "$!\n";
my $retval =  $?;
# print "retval-> $retval<br />\n";

print "Content-Disposition: attachment; filename='testPDF.pdf'\n";
print "Content-type: application/octet-stream\n\n";
print $pdf;

        [download]
[reply]
[d/l]
Re: perl wkhtmltopdf Error: Unable to write to destination
by choroba (Cardinal) on May 07, 2014 at 16:19 UTC
    Crossposted at StackOverflow. It is considered polite to inform about crossposting, so people not attending both sites don't waste their time hacking a solution to a problem already solved at the other end of the Internets.

    Also, googling for the error message brings up this link. Is it helpful?

    لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ
[reply]

      Thank you. I did not know about the rule about cross posting.

      The link related to windows specifically so I wasn't able to use it.

[reply]

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