Internal Server Error with very simple python script

Question

I'm new to python, and i'm trying to run a simple script (On a Mac if that's important).

Now, this code, gives me Internal Server Error:

#!/usr/bin/python

print 'hi'

But this one works like a charm (Only extra 'print' command):

#!/usr/bin/python
print

print 'hi'

Any explanation? Thanks!

Update:

When I run this script from the Terminal everything is fine. But when I run it from the browser:

http://localhost/cgi-bin/test.py

I get this error (And again, only if i'm not adding the extra print command). I use Apache server of course.

I'm surprised you get an "internal server error" when running a simple script. I noticed the 'apache' tag but that doesn't say anything about the way you actually run your script... — Ioan Alexandru Cucu
– Ioan Alexandru Cucu, Commented Nov 19, 2013 at 19:26

robertklep · Accepted Answer · 2013-11-19 19:43:56Z

6

~~Looks like you're running your script as a CGI-script~~ (your edit confirms that you're using CGI)

...and the initial (empty) print is required to signify the end of the headers.

Check your Apache's error log (/var/log/apache2/error.log probably) to see if it says 'Premature end of script headers' (more info here).

EDIT: a bit more explanation:

A CGI script in Apache is responsible for generating it's own HTTP response.

An HTTP response consists of a header block, an empty line, and the so-called body contents. Even though you should generate some headers, it's not mandatory to do so. However, you do need to output the empty line; Apache expects it to be there, and if it's not (or if you only output a body which can't be parsed as headers), Apache will generate an error.

That's why your first version didn't work, but your second did: adding the empty print added the required empty line that Apache was expecting.

This will also work:

#!/usr/bin/env python

print "Content-Type: text/html"  # header block
print "Vary: *"                  # also part of the header block
print "X-Test: hello world"      # this too is a header, but a made-up one
print                            # empty line
print "hi"                       # body

edited Nov 19, 2013 at 19:43

answered Nov 19, 2013 at 19:28

robertklep

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2 Comments

Avi Tsadok Over a year ago

Hi, Thanks. I checked, and it says 'malformed header from script. Bad header=hi: test.py'. What does it mean?

tripleee Over a year ago

That the script's output is not valid for CGI. It should output valid HTTP headers before its regular output.

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