From: "Ara.T.Howard" <Ara.T.Howard@...>
Date: 2005-05-23T07:00:17+09:00
Subject: Re: Ruby and CGI error 500

On Sun, 22 May 2005, greyfade@gmail.com wrote:

> this is a problem that's been driving me nuts ever since i first tried it.
>
> i can create simple, minimal scripts in Python, Perl, and PHP that run
> flawlessly on the first try with minimal effort, both on my local testing
> system (Apache 2.0.52 and Ruby 1.8.2) and on the server my personal site is
> hosted on (Apache 1.3.33 and unknown version of Ruby - i'm trying to find
> out).  but no matter what i try, i simply can not get even the most minimal
> ruby script to function:
>
> #!/usr/bin/env ruby
>
> print "Content-type: text/html\n\n"
> print "<html><body>Hello World!</body></html>\n"
>
> it runs perfectly fine at the console, no warnings, no errors, no problems.
> but as a CGI script, it's another story:  i get an error 500 and the cryptic
> (and seemingly common) "Premature end of script headers".  no other warnings
> or errors.  if i simply change "ruby" to "python" on the shebang line, the
> above script magically works with no other effort on my part.

nothing magic about it:

   [ahoward@localhost ~]$ cat a.rb
   #!/usr/bin/env ruby
   print "Content-type: text/html\n\n"
   print "<html><body>Hello World!</body></html>\n"

   [ahoward@localhost ~]$ cat a.py
   #!/usr/bin/env python
   print "Content-type: text/html\n\n"
   print "<html><body>Hello World!</body></html>\n"

   [ahoward@localhost ~]$ a.rb | od -c > a.rb.out

   [ahoward@localhost ~]$ a.py | od -c > a.py.out

   [ahoward@localhost ~]$ diff -u a.rb.out a.py.out
   --- a.rb.out    2005-05-21 17:58:33.000000000 -0600
   +++ a.py.out    2005-05-21 17:58:35.000000000 -0600
   @@ -1,5 +1,6 @@
    0000000   C   o   n   t   e   n   t   -   t   y   p   e   :       t   e
   -0000020   x   t   /   h   t   m   l  \n  \n   <   h   t   m   l   >   <
   -0000040   b   o   d   y   >   H   e   l   l   o       W   o   r   l   d
   -0000060   !   <   /   b   o   d   y   >   <   /   h   t   m   l   >  \n
   -0000100
   +0000020   x   t   /   h   t   m   l  \n  \n  \n   <   h   t   m   l   >
   +0000040   <   b   o   d   y   >   H   e   l   l   o       W   o   r   l
   +0000060   d   !   <   /   b   o   d   y   >   <   /   h   t   m   l   >
   +0000100  \n  \n
   +0000102

or, put another way:

   harp:~ > ruby -e 'print 42' | od -c
   0000000   4   2
   0000002

   harp:~ > python -c 'print 42' | od -c
   0000000   4   2  \n
   0000003


so you were just lucky that python and perl were sending you 'extra' newline.
you'd have even more issues if you did something like on a unix vs windows box
and it's the reason cgi abstraction are made.

this will work no matter what platform:

   [ahoward@localhost ~]$ cat a.rb
   #!/usr/bin/env ruby
   require 'cgi'
   CGI::new.out{ "<html><body>Hello World!</body></html>\n" }

   [ahoward@localhost ~]$ ruby a.rb < /dev/null
   Content-Type: text/html
   Content-Length: 39

   <html><body>Hello World!</body></html>
   [ahoward@localhost ~]$ ruby a.rb < /dev/null | od -c
   0000000   C   o   n   t   e   n   t   -   T   y   p   e   :       t   e
   0000020   x   t   /   h   t   m   l  \r  \n   C   o   n   t   e   n   t
   0000040   -   L   e   n   g   t   h   :       3   9  \r  \n  \r  \n   <
   0000060   h   t   m   l   >   <   b   o   d   y   >   H   e   l   l   o
   0000100       W   o   r   l   d   !   <   /   b   o   d   y   >   <   /
   0000120   h   t   m   l   >  \n
   0000126


you'll also note that cgis are supposed to send '\r\n' not '\n\n' so the other
two never really should have worked anyhow ;-)

> i'm going insane because nothing, AFAICT, is wrong.  the server is correctly
> set-up, permissions are correct, ownership is correct, ruby is installed and
> working, yet NOTHING seems to coax it into working.  it repeatedly reports
> this incredibly uninformative "Premature end of script headers" error.

this is because the script headers prematurely ended before the content started
since \r\n was never seen ;-)

> is there something i could have missed?  a possible misconfiguration?  or
> does ruby just hate me?

doubtful ;-)

-a
-- 
===============================================================================
| email :: ara [dot] t [dot] howard [at] noaa [dot] gov
| phone :: 303.497.6469
| My religion is very simple.  My religion is kindness.
| --Tenzin Gyatso
===============================================================================