Help for a beginner trying to use python 3 and cgi

natibo · 04-20-2016, 11:06 AM

First of all, I have searched the forums and tried just about everything I have found.
Second:
my OS is Linux Mint 17.4
I'm using python 3.4
Apache2 (which I admit I know nothing about but downloaded to try to get this to work)
I have tried all of the suggestions at this site https://www.linux.com/blog/configuri...python-scripts

I have gone through Mark Lutz's book "Learning Python.
I am know going through his book "Python Programming". I know it is dated and I know his examples are more "Windows" centric, but oh well. I'm a 50 year old enginner who is home recovering from surgery and thought I would learn Python.

Program 1 executed from working directory and pulled up by firefox after double clicking:
cgi101.htlm

Code:

<html>
<title>Interactive Page</title>
<body>
<form method=POST action="cgi-bin/cgi101.py">
    <P><B>Enter your name:</B>
    <P><input type=text name=user>
    <P><input type=submit>
</form>
</body></html>

Here is the second program located in the cgi-bin sub-directory of the working directory:

Code:

#!/usr/bin/env python3 (this file was made executable by chmod)

# -*- coding: UTF-8 -*-# enable debugging

import cgi, cgitb
cgitb.enable()
form = cgi.FieldStorage()                 # parse form data
print('Content-type: text/html\n')        # hdr plus blank line
print('<title>Reply Page</title>')        # html reply page
if not 'user' in form:
    print('<h1>Who are you?</h1>')
else:
    print('<h1>Hello <i>%s</i>!</h1>' % cgi.escape(form['user'].value))

This is what I get:
https://goo.gl/photos/DR1dYxUwQUYBwMAp9

If you can't see the picture firefox has a pop up window asking me what firefox should do with this file.
Here is my apache2.conf file

Code:

# This is the main Apache server configuration file. It contains the
# configuration directives that give the server its instructions.
# See http://httpd.apache.org/docs/2.4/ for detailed information about
# the directives and /usr/share/doc/apache2/README.Debian about Debian specific
# hints.
#
#
# Summary of how the Apache 2 configuration works in Debian:
# The Apache 2 web server configuration in Debian is quite different to
# upstream's suggested way to configure the web server. This is because Debian's
# default Apache2 installation attempts to make adding and removing modules,
# virtual hosts, and extra configuration directives as flexible as possible, in
# order to make automating the changes and administering the server as easy as
# possible.

# It is split into several files forming the configuration hierarchy outlined
# below, all located in the /etc/apache2/ directory:
#
# /etc/apache2/
# |-- apache2.conf
# | `-- ports.conf
# |-- mods-enabled
# | |-- *.load
# | `-- *.conf
# |-- conf-enabled
# | `-- *.conf
# `-- sites-enabled
# `-- *.conf
#
#
# * apache2.conf is the main configuration file (this file). It puts the pieces
# together by including all remaining configuration files when starting up the
# web server.
#
# * ports.conf is always included from the main configuration file. It is
# supposed to determine listening ports for incoming connections which can be
# customized anytime.
#
# * Configuration files in the mods-enabled/, conf-enabled/ and sites-enabled/
# directories contain particular configuration snippets which manage modules,
# global configuration fragments, or virtual host configurations,
# respectively.
#
# They are activated by symlinking available configuration files from their
# respective *-available/ counterparts. These should be managed by using our
# helpers a2enmod/a2dismod, a2ensite/a2dissite and a2enconf/a2disconf. See
# their respective man pages for detailed information.
#
# * The binary is called apache2. Due to the use of environment variables, in
# the default configuration, apache2 needs to be started/stopped with
# /etc/init.d/apache2 or apache2ctl. Calling /usr/bin/apache2 directly will not
# work with the default configuration.

# Global configuration
#

#
# ServerRoot: The top of the directory tree under which the server's
# configuration, error, and log files are kept.
#
# NOTE! If you intend to place this on an NFS (or otherwise network)
# mounted filesystem then please read the Mutex documentation (available
# at <URL:http://httpd.apache.org/docs/2.4/mod/core.html#mutex>);
# you will save yourself a lot of trouble.
#
# Do NOT add a slash at the end of the directory path.
#
#ServerRoot "/etc/apache2"

#
# The accept serialization lock file MUST BE STORED ON A LOCAL DISK.
#
Mutex file:${APACHE_LOCK_DIR} default

#
# PidFile: The file in which the server should record its process
# identification number when it starts.
# This needs to be set in /etc/apache2/envvars
#
PidFile ${APACHE_PID_FILE}

#
# Timeout: The number of seconds before receives and sends time out.
#
Timeout 300

#
# KeepAlive: Whether or not to allow persistent connections (more than
# one request per connection). Set to "Off" to deactivate.
#
KeepAlive On

#
# MaxKeepAliveRequests: The maximum number of requests to allow
# during a persistent connection. Set to 0 to allow an unlimited amount.
# We recommend you leave this number high, for maximum performance.
#
MaxKeepAliveRequests 100

#
# KeepAliveTimeout: Number of seconds to wait for the next request from the
# same client on the same connection.
#
KeepAliveTimeout 5

#Bo Edit

ServerName localhost
<Directory "/home/*/public_html">
Options +ExecCGI
AddHandler cgi-script .cgi
</Directory>

<Directory "/home/Dropbox/apache2">
Options +ExecCGI
SetHandler cgi-script
</Directory>

<Directory "/home/Dropbox/apache2">
Options +ExecCGI
AddHandler cgi-script .py
</Directory>

ScriptAlias "/cgi-bin/" "/var/www/html/cgi-bin"
<Directory "/var/www/html/cgi-bin">
AllowOverride None
Options +ExecCGI +MultiViews +SymLinksIfOwnerMatch +Includes +Multiviews
Order allow,deny
Allow from all
AddHandler cgi-script .py
AddHandler cgi-script .cgi
AddHandler wsgi-script .wsgi
</Directory>

AddHandler cgi-script .cgi

# These need to be set in /etc/apache2/envvars
User ${APACHE_RUN_USER}
Group ${APACHE_RUN_GROUP}

#
# HostnameLookups: Log the names of clients or just their IP addresses
# e.g., www.apache.org (on) or 204.62.129.132 (off).
# The default is off because it'd be overall better for the net if people
# had to knowingly turn this feature on, since enabling it means that
# each client request will result in AT LEAST one lookup request to the
# nameserver.
#
HostnameLookups Off

# ErrorLog: The location of the error log file.
# If you do not specify an ErrorLog directive within a <VirtualHost>
# container, error messages relating to that virtual host will be
# logged here. If you *do* define an error logfile for a <VirtualHost>
# container, that host's errors will be logged there and not here.
#
ErrorLog ${APACHE_LOG_DIR}/error.log

#
# LogLevel: Control the severity of messages logged to the error_log.
# Available values: trace8, ..., trace1, debug, info, notice, warn,
# error, crit, alert, emerg.
# It is also possible to configure the log level for particular modules, e.g.
# "LogLevel info ssl:warn"
#
LogLevel warn

# Include module configuration:
IncludeOptional mods-enabled/*.load
IncludeOptional mods-enabled/*.conf

# Include list of ports to listen on
Include ports.conf

# Sets the default security model of the Apache2 HTTPD server. It does
# not allow access to the root filesystem outside of /usr/share and /var/www.
# The former is used by web applications packaged in Debian,
# the latter may be used for local directories served by the web server. If
# your system is serving content from a sub-directory in /srv you must allow
# access here, or in any related virtual host.
<Directory />
Options FollowSymLinks
AllowOverride None
Require all denied
</Directory>

<Directory /usr/share>
AllowOverride None
Require all granted
</Directory>

<Directory /var/www/>
Options Indexes FollowSymLinks
AllowOverride None
Require all granted
</Directory>

#<Directory /srv/>
# Options Indexes FollowSymLinks
# AllowOverride None
# Require all granted
#</Directory>

# AccessFileName: The name of the file to look for in each directory
# for additional configuration directives. See also the AllowOverride
# directive.
#
AccessFileName .htaccess

#
# The following lines prevent .htaccess and .htpasswd files from being
# viewed by Web clients.
#
<FilesMatch "^\.ht">
Require all denied
</FilesMatch>

#
# The following directives define some format nicknames for use with
# a CustomLog directive.
#
# These deviate from the Common Log Format definitions in that they use %O
# (the actual bytes sent including headers) instead of %b (the size of the
# requested file), because the latter makes it impossible to detect partial
# requests.
#
# Note that the use of %{X-Forwarded-For}i instead of %h is not recommended.
# Use mod_remoteip instead.
#
LogFormat "%v:%p %h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\"" vhost_combined
LogFormat "%h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\"" combined
LogFormat "%h %l %u %t \"%r\" %>s %O" common
LogFormat "%{Referer}i -> %U" referer
LogFormat "%{User-agent}i" agent

# Include of directories ignores editors' and dpkg's backup files,
# see README.Debian for details.

# Include generic snippets of statements
IncludeOptional conf-enabled/*.conf

# Include the virtual host configurations:
IncludeOptional sites-enabled/*.conf

# vim: syntax=apache ts=4 sw=4 sts=4 sr noet

I have spent about 2 days trying to get this to work. Any help would be appreciated.

HMW · 04-20-2016, 11:34 AM

Quote:

Originally Posted by natibo

Code:

#!/usr/bin/env python3 (this file was made executable by chmod)

# -*- coding: UTF-8 -*-# enable debugging

import cgi, cgitb
cgitb.enable()
form = cgi.FieldStorage()                 # parse form data
print('Content-type: text/html\n')        # hdr plus blank line
print('<title>Reply Page</title>')        # html reply page
if not 'user' in form:
    print('<h1>Who are you?</h1>')
else:
    print('<h1>Hello <i>%s</i>!</h1>' % cgi.escape(form['user'].value))

This might be unrelated, but you can't use a '\n' like that when you print to html, you ought to do like this:

Code:

print('Content-type: text/html<br />')

I have only used Python for cgi stuff once, and although it works, there are upsides (imho) to using php in combination with apache.

I wish I could be of more help, sorry!
HMW

grail · 04-20-2016, 11:40 AM

So I am sure one of the Apache gurus will straighten this out for you, but looking at the link you provided I noticed a couple of differences (which may or may not be an issue).

1. You listed the same directory path for the SetHandler and AddHandler for your cgi-scripts, but in the example on the link the SetHandler is actually one level further down the same path as AddHandler:

Code:

<Directory /srv/www/yoursite/public_html/cgi-bin>
        Options ExecCGI
        SetHandler cgi-script
    </Directory>

<Directory /srv/www/yoursite/public_html>
        Options +ExecCGI
        AddHandler cgi-script .py
    </Directory>

2. In the SetHandler section there is no '+' before ExecCGI

Both of these might be nothing, but maybe try exactly the same first and then start making changes?

dugan · 04-20-2016, 04:25 PM

Quote:

Originally Posted by hmw

this might be unrelated, but you can't use a '\n' like that when you print to html, you ought to do like this:

Code:

print('content-type: Text/html<br />')

i have only used python for cgi stuff once, and although it works, there are upsides (imho) to using php in combination with apache.

I wish i could be of more help, sorry!
Hmw

You use "\n" in the HTTP header and "<br>" in the HTML section. The "Content-Type" line would be part of the HTTP header and therefore should use "\n".

I'd question whether that line is needed though.

HMW · 04-21-2016, 01:33 AM

Quote:

Originally Posted by dugan

You use "\n" in the HTTP header and "<br>" in the HTML section. The "Content-Type" line would be part of the HTTP header and therefore should use "\n".

I'd question whether that line is needed though.

Yes. Of course. dugan is absolutely right. My bad.

Best regards,
HMW

cnamejj · 04-21-2016, 03:33 AM

One thing that I would change. There needs to be a blank line between the "Content-type:" header line and the HTML itself.

Also, technically the header lines are supposed to be terminated by a CR and LF. So I would use this.

Code:

print('Content-type: text/html\r\n\r\n', end='')

What you have coded does add two '\n' characters, but it's not as clear from reading the code.

OK, I re-checked the attached photo. It's hard to read on this screen, since the type is a little small for my "not so great anymore" eyes.

But here's a question. It looks like the URL in your browser is "file:///home/Dropbox/PyProg/Preview/cgi101.html" and the post target in the form is "cgi-bin/cgi101.py". If that's how you're loading the form and submitting it, then you're not sending the request to your webserver. It's just reading the FILE at the location where the script lives.

You should either pull the HTML up through a URL that hits your Apache server, meaning it should start with "http://..." or you can change the form to have a post action that starts with "http://...".

natibo · 04-21-2016, 07:24 AM

cnamejj,

Of all of the forums I have posted on, I believe you are on to something. I believe it is something reall simple and stupid. If you could expand on what you said. I am not familiar with apache nor html.

cnamejj · 04-22-2016, 02:11 AM

If you're writing CGI scripts, then you need to invoke them by making a request to a webserver. The Apache configs you posted direct that software to recognize certain paths in a request as being requests to run programs, as opposed to sending a static file.

So a URL like "http://some.domain.com/cgi-bin/MyPyProgram.py" might run the program called "MyPyProgram.py" and send back the output. Whereas a URL like "http://some.domain.com/category/interesting.html" probably just sends a copy of the file called "interesting.html".

But the key here is that Apache is interpreting the requests and deciding what's appropriate. In a browser entering a URL like "file:///path/filename" doesn't involve a webserver. The browser just shows you the contents of the local file you call out. So if you ask for a CGI script, the browser will just show you the script and not run it.

natibo · 04-22-2016, 01:01 PM

So you have all my code. How would you fix this?

norobro · 04-22-2016, 07:07 PM

As cnamejj said above you need to point your browser at your webserver.

If you are on the same machine as the server try entering "localhost/cgi101.html" or "127.0.0.1/cgi101.html" on the address bar.

If you are on a LAN, you can enter the ip of the machine the server is running on. For example, the ip of my server is 192.168.2.3 so with your setup I would access the file from any machine on the LAN by typing "192.168.2.3/cgi101.html"

HTH