Python CGI Issue

felix001 · 07-17-2011, 02:23 PM

Does anyone know how to run a linux command from a Python CGI script. Im currently trying :

Code:

#!/usr/bin/python

# Import modules for CGI handling
import cgi, cgitb
import os
from subprocess import call

print "Content-type:text/html\r\n\r\n"
print '<html>'
print '<head>'
print '<title>Hello Word - First CGI Program</title>'
print '</head>'
print '<body>'
print "<p>",call(["ls", "-l"]),"</p>"
print '</body>'
print '</html>'

.. but I keep getting an error within my apache logs saying Malformed Header.

Has anyone any ideas ??

theNbomr · 07-17-2011, 04:10 PM

Just a shot: remove the CR's from your Content-type line.
--- rod.

felix001 · 07-18-2011, 12:20 AM

Tried that but same issue. The stange thing is if I run this code but call an echo 123 it errors with malformed header 123. If I use a print "123" it works. It's like the system call is echo out the output before the header (???)

theNbomr · 07-18-2011, 09:06 AM

Okay, then use telnet or netcat to issue an HTTP request from a URL that 'works', even a static page. Compare that to the output of your Python script when run from a shell as a stand-alone program. The difference(s) should be fairly obvious.
Perhaps Python is complaining about some of your module imports.
--- rod.

felix001 · 07-18-2011, 02:11 PM

I found a way in which to get this to work and it was to use the -u switch within my shabang. Does anyone know what this actually does.

NOT WORKING
[

Code:

root@webserver1 ~]# python /var/www/cgi-bin/hello_get2.py
Content-type: text/html


<html>
<head>
<title>Hello Word - First CGI Program</title>
</head>
<body><p>
123
[Querying whois.arin.net]
[whois.arin.net]

WORKING

Code:

[root@webserver1 ~]# python /var/www/cgi-bin/hello_get.py
Content-type: text/html


<html>
<head>
<title>Hello Word - First CGI Program</title>
</head>
<body><p>

WORKING

Code:

[root@webserver1 ~]# curl http://127.0.0.1/cgi-bin/hello_get.py

<html>
<head>
<title>Hello Word - First CGI Program</title>
</head>
<body><p>
123

Tinkster · 07-18-2011, 04:03 PM

According to the python man-page (very much worthwhile reading, btw!):

Code:

       -u     Force stdin, stdout and stderr to  be  totally  unbuffered.   On
              systems  where  it matters, also put stdin, stdout and stderr in
              binary mode.  Note that there is internal  buffering  in  xread-
              lines(),  readlines()  and  file-object  iterators ("for line in
              sys.stdin") which is not influenced by  this  option.   To  work
              around  this, you will want to use "sys.stdin.readline()" inside
              a "while 1:" loop.

Cheers,
Tink

felix001 · 07-18-2011, 05:24 PM

I had read this before but im not really sure why I need to add it.

Tinkster · 07-18-2011, 08:18 PM

Quote:

Originally Posted by felix001

I had read this before but im not really sure why I need to add it.

Not sure how call works, but I could get it to play nice w/o -u
and the use of the following Popen:

Code:

#!/usr/bin/python

# Import modules for CGI handling
import cgi, cgitb
import os
import subprocess

child=subprocess.Popen(['ls','-l'], stdout=subprocess.PIPE )
print "Content-type:text/html\r\n\r\n"
print '<html>'
print '<head>'
print '<title>Hello Word - First CGI Program</title>'
print '</head>'
print '<body>'
print "<p>","<br>".join(child.stdout.readlines()),"</p>"
print '</body>'
print '</html>'

Mind you, the spacing for the ls output is clobbered.

Cheers,
Tink