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

My cgi program generated a file. I want to put this file as a link on the web so that users can click the link to download. This seems to be such a common task on the web. Would anybody please show me a script example? When I searched CPAN for perl modules, it always points me to the lwp-download. To do this on the command line is straight forward, but how do I put this command in a url? Thanks,

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Re: File Download from Web
by TomDLux (Vicar) on Mar 12, 2004 at 01:28 UTC

    How about simply putting a URL on a web page linking to the text file: 

    <a href="file.txt">My newly generated file</a>

    [download]

    --
    TTTATCGGTCGTTATATAGATGTTTGCA

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Re: File Download from Web
by esskar (Deacon) on Mar 12, 2004 at 02:38 UTC
    lets say your script is generating a gif
    #!/usr/bin/perl
# script.pl
use strict;
use warnings;

my $gif = pack("H*",
               '47494638396101000100B30000888888' .
               'FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF' .
               'FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF' .
               'FFFFFFFFFFFFFFFFFFFFFFFFFF2C0000' .
               '0000010001000004021044003B'
              );
print "Content-Type: image/gif\n\n";
binmode STDOUT;
print $gif;

    [download]
    then just add to your web page as pointed out above 
    <a href="script.pl">A Gif</a>

    [download]
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Re: File Download from Web
by jiewho (Novice) on Mar 12, 2004 at 08:03 UTC
    Thanks for the input. Both methods are to have the file displayed in the browser window. But this is not what I meant. When a user clicks the link, I want a file download dialogue window to pop up, so the user can save this file to the local computer. This automatically happens when the file is a .tar.gz type file. But if the file is a .txt file, it's displayed in the browser window. So is there a way not to have the .txt file displayed but to pop up a file download dialogue window when the link is clicked? Thanks
[reply]
      Your program needs to send the file to the user itself. When you click a link you are linking to the program and not to the file, something like: 
      <a href="/yourprogram.cgi">Click here</a>

      [download]
      The program must spit out the correct headers. One of these should probably be 'content-disposition' so I suggest you poke around based on that.

      Be wary of specifiying the file in the link unless you know EXACTLY what you are doing, otherwise this can happen: 
      <a href="file.cgi?file=../../../etc/passwd">here</a>

      [download]
      Ok thats a contrived example to indicated what I mean but that should indicate the problems you face ;). If you are not careful someone could download any file on your system which is something you definitely wouldn't want :).
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[select]
      okay... then use 
      print "Content-Type: application/octet-stream\n\n";

      [download]
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Re: File Download from Web
by wolfi (Scribe) on Mar 12, 2004 at 09:55 UTC
    not really perl-solutions, but after some thought -
    well... changing the mime-types won't work, since some browsers disregard this in favour of their own results from their pre-scanning of the file - and changing the extension of the file would probably confuse visitors... or scare'em.
    setting up some ftp-thingee might be a thought - but really ->
    the easiest thing you can do is to compress it (if you don't wanna use tar.gz - use WinZip - or better yet, have both options available). Zipped files are always (i would think) downloaded like ya want.
    OR... simply put a link to the document and tell your users, that if they'd like a copy - they should right-click on the link and select SAVE TARGET AS (or whatever). That'd be the easiest.
[reply]

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