Re: [Tutor] CGI File Woes
The best way to debug cgi is to tail the server log when you don't get commandline output. This will give you a clue to what is happening.. shoulld be something like /var/log/apache or something like that... Eric wormwood_3 [EMAIL PROTECTED] wrote: Hello all, I am working on a very simple CGI script. The site I want to use it on is a shared linux host, but I confirmed that .py files in the right dir with the right permissions and shebang execute just fine, Hello World sort of tests were successful. So now something a little more involved: #!/usr/bin/python2.4 import cgitb; cgitb.enable() thefile = open(template.html, r) templatestuff = thefile.read() thefile.close() print Content-Type: text/html if templatestuff: print Found it title1 = I am a title! body1 = I am some hot content print templatestuff % (title1, body1) template.html is in the same dir, and is simply: http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd; %s %s If I run this script without the 3 lines after the import line, it works fine (namely I get an error that templatestuff is not defined, as would be expected). With those lines however, I am getting a 500 Internal Server Error. Since I am not shown an error page with cgitb, this would likely mean a syntax error. However, if I run the script locally, it works just fine, printing out the HTML with variables filled in. Now for the odd part: If I change that open line to thefile = open(asdas, r), I get IOError: [Errno 2] No such file or directory: 'asdas' . So it seems the script is finding the template file when I have it as above, but is throwing something when it tries to open it. I have confirmed the file has the right permissions, I have even tried it with all permissions set on that file. I am just totally baffled why I cannot open any files from the script. Any ideas? -Sam ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor - Catch up on fall's hot new shows on Yahoo! TV. Watch previews, get listings, and more!___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] CGI File Woes
wormwood_3 [EMAIL PROTECTED] wrote #!/usr/bin/python2.4 import cgitb; cgitb.enable() thefile = open(template.html, r) templatestuff = thefile.read() thefile.close() print Content-Type: text/html if templatestuff: print Found it title1 = I am a title! body1 = I am some hot content print templatestuff % (title1, body1) template.html is in the same dir, and is simply: http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd; html html Did you mean for there to be two html tags or is it a typo? head title %s /title /head body %s /body /html If I run this script without the 3 lines after the import line, it works fine (namely I get an error that templatestuff is not defined, I am getting a 500 Internal Server Error. Since I am not shown an error page with cgitb, this would likely mean a syntax error. I've never used gcitb (and until now didn't know it existed!) so can't comment. But I usually see this when the web user doesn't have permission to open the html file. But... I have confirmed the file has the right permissions, I have even tried it with all permissions set on that file. For all users? Remember that the web server runs as a separate user and that's the user than needs to open the file. HTH, -- Alan Gauld Author of the Learn to Program web site http://www.freenetpages.co.uk/hp/alan.gauld ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] CGI File Woes
Remember, you can always add more logging that goes to your own log file. Have it open a file in /tmp and write out a log of what's happening. Wrap your main code block in an exception handler, etc. Have it print out the exception to the log file. This will allow you to look and see what the error is rather than speculating about it. --Michael On 9/30/07, wormwood_3 [EMAIL PROTECTED] wrote: Hello all, I am working on a very simple CGI script. The site I want to use it on is a shared linux host, but I confirmed that .py files in the right dir with the right permissions and shebang execute just fine, Hello World sort of tests were successful. So now something a little more involved: #!/usr/bin/python2.4 import cgitb; cgitb.enable() thefile = open(template.html, r) templatestuff = thefile.read() thefile.close() print Content-Type: text/html if templatestuff: print Found it title1 = I am a title! body1 = I am some hot content print templatestuff % (title1, body1) template.html is in the same dir, and is simply: http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd; html html head title %s /title /head body %s /body /html If I run this script without the 3 lines after the import line, it works fine (namely I get an error that templatestuff is not defined, as would be expected). With those lines however, I am getting a 500 Internal Server Error. Since I am not shown an error page with cgitb, this would likely mean a syntax error. However, if I run the script locally, it works just fine, printing out the HTML with variables filled in. Now for the odd part: If I change that open line to thefile = open(asdas, r), I get IOError: [Errno 2] No such file or directory: 'asdas' . So it seems the script is finding the template file when I have it as above, but is throwing something when it tries to open it. I have confirmed the file has the right permissions, I have even tried it with all permissions set on that file. I am just totally baffled why I cannot open any files from the script. Any ideas? -Sam ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor -- Michael Langford Phone: 404-386-0495 Consulting: http://www.TierOneDesign.com/ Entertaining: http://www.ThisIsYourCruiseDirectorSpeaking.com ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] CGI File Woes
Did you mean for there to be two html tags or is it a typo? Just a typo. Should not have a big effect, but it has been fixed. I've never used cgitb (and until now didn't know it existed!) so can't comment. I had not heard of it until this week when I started working on CGI stuff, but I have found it super handy! All you have to do it import cgitb; cgitb.enable() and all tracebacks will get printed to nicely formatted HTML output on the page you were trying to load. But I usually see this when the web user doesn't have permission to open the html file. But... This definitely would make the most sense in that the error is not a Python error, at least I am assuming so from the lack of traceback. However, the odd thing is that if I hit template.html directly, the page renders just fine. This would mean the web user can access it, right? And I was assuming the Python script was being run by the web user as well, but perhaps it is not. For all users? Remember that the web server runs as a separate user and that's the user than needs to open the file. Sorry, I stated that poorly. What I meant was that in the process of troubleshooting, I ended up enabling ALL permissions, so user, group, and others could read, write, and execute. So since this is now the case, and the script runs fine locally, and I can hit template.html on its own on the web server... I am still quite baffled! -Sam ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] CGI File Woes
wormwood_3 [EMAIL PROTECTED] wrote I had not heard of it until this week when I started working on CGI stuff, but I have found it super handy! All you have to do it import cgitb; cgitb.enable() and all tracebacks will get printed to nicely formatted HTML output on the page you were trying to load. Ok, Heres a thought. try forcing an error after opening the file. See what the traceback says. You can add a message string to an exception so that it will print... class LogError(Exception): pass raise LogError, Any old text here So you force the cgitb to kick in and print the mesage you specify, use it like a print statement to debug whats happening... Its a bit laborious but better than nothing! See if that helps Alan G ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] CGI File Woes
wormwood_3 wrote: Hello all, I am working on a very simple CGI script. The site I want to use it on is a shared linux host, but I confirmed that .py files in the right dir with the right permissions and shebang execute just fine, Hello World sort of tests were successful. Those are the first things I'd try too. So now something a little more involved: #!/usr/bin/python2.4 import cgitb; cgitb.enable() thefile = open(template.html, r) templatestuff = thefile.read() thefile.close() print Content-Type: text/html if templatestuff: print Found it title1 = I am a title! body1 = I am some hot content print templatestuff % (title1, body1) template.html is in the same dir, and is simply: http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd; html html head title %s /title /head body %s /body /html [..] Any ideas? Here are a few ideas plus some suggestions. I've been dabbling with python/cgi myself and so there might be something you can take from these comments. - If your webserver and the machine where you executed this from are different (home directories are NFS mounts etc.), then the permissions and directory visibilities might affect things. - It looks fairly obvious that the problem is in those three lines. Your content-type header is printed only after those lines are executed so if there is an error there, you'll get an error 500. Try putting your content-type line right after your import cgitb. - Wrap the 3 suspicious lines in a try block and print out the execption which you catch. - Tail the server logs to see what happened. Good luck. -- ~noufal ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] CGI File Woes
wormwood_3 wrote: I've never used cgitb (and until now didn't know it existed!) so can't comment. I had not heard of it until this week when I started working on CGI stuff, but I have found it super handy! All you have to do it import cgitb; cgitb.enable() and all tracebacks will get printed to nicely formatted HTML output on the page you were trying to load. No doubt cgitb is a great tool for debugging cgi, but IIUC there are at least two instances when you will not get the pretty printed tracebacks in the browser when using cgitb. One is after, what I would call, a 'compile time' exception such as SyntaxError, in your python code. The other is when the python code runs without exception, but you have not separated the header and the document content with a newline. At least, I have found these to be true when using apache-cgi. Consider the following examples: #!/usr/bin/env python # raises a SyntaxError import cgi import cgitb; cgitb.enable() print Content-type: text/html\n\n # NOTE: purposeful misspelling of the print statement prin htmlbodypHello, world!/p/body/html # the code above will produce a server 500, with apache # complaining about premature end of script headers ... #!/usr/bin/env python # good python, bad data import cgi import cgitb; cgitb.enable() print Content-type: text/html print htmlbodypHello, world!/p/body/html # this is syntactically correct python, and will # run from the command line, but the html header # and html content have no separation, so apache # will consider all of it to be header info, resulting # in another server 500, malformed header As others have advised, under these circumstances you can review the apache error log (if your webhost allows it). Or roll-your-own logging equivalent, and run your cgi from a terminal to catch SyntaxErrors and the like. HTH, Marty ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] CGI File Woes
Those examples were a lot of help Martin. Turned out the only issue was that I did not have this line right: print Content-type: text/html\n\n With that form, it loaded just fine. It had been running fine from the terminal, but without this line being right, Apache did not know what to do with it. I had spoken with my web-hosting provider, but since I had a shared account I was unable to view the server logs. And the person helping me knew nothing about Python (he kept slipping and calling it PHP actually, to my dismay and chagrin:-) ). Thanks for all the help, Alan and Martin. -Sam _ - Original Message From: Martin Walsh [EMAIL PROTECTED] To: tutor@python.org Sent: Sunday, September 30, 2007 1:07:02 PM Subject: Re: [Tutor] CGI File Woes No doubt cgitb is a great tool for debugging cgi, but IIUC there are at least two instances when you will not get the pretty printed tracebacks in the browser when using cgitb. One is after, what I would call, a 'compile time' exception such as SyntaxError, in your python code. The other is when the python code runs without exception, but you have not separated the header and the document content with a newline. At least, I have found these to be true when using apache-cgi. Consider the following examples: #!/usr/bin/env python # raises a SyntaxError import cgi import cgitb; cgitb.enable() print Content-type: text/html\n\n # NOTE: purposeful misspelling of the print statement prin htmlbodypHello, world!/p/body/html # the code above will produce a server 500, with apache # complaining about premature end of script headers ... #!/usr/bin/env python # good python, bad data import cgi import cgitb; cgitb.enable() print Content-type: text/html print htmlbodypHello, world!/p/body/html # this is syntactically correct python, and will # run from the command line, but the html header # and html content have no separation, so apache # will consider all of it to be header info, resulting # in another server 500, malformed header As others have advised, under these circumstances you can review the apache error log (if your webhost allows it). Or roll-your-own logging equivalent, and run your cgi from a terminal to catch SyntaxErrors and the like. HTH, Marty ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] CGI File Woes
wormwood_3 wrote: Those examples were a lot of help Martin. Turned out the only issue was that I did not have this line right: print Content-type: text/html\n\n Sam, Glad the examples helped. I should probably fess up and point out that I mistakenly added an additional newline to that print statement. You only need one, as the print itself will append an extra. So by adding the addition \n, a blank line will be sent to the browser as part of the page content, which shouldn't be a problem for text/html content-types. But as soon as you want to serve up another content-type (eg. image/png) you may run into odd problems. So, the corrected print statement should look like this: print Content-type: text/html\n or as described in the docs, http://docs.python.org/lib/cgi-intro.html print Content-type: text/html print HTH, Marty With that form, it loaded just fine. It had been running fine from the terminal, but without this line being right, Apache did not know what to do with it. I had spoken with my web-hosting provider, but since I had a shared account I was unable to view the server logs. And the person helping me knew nothing about Python (he kept slipping and calling it PHP actually, to my dismay and chagrin:-) ). Thanks for all the help, Alan and Martin. -Sam _ - Original Message From: Martin Walsh [EMAIL PROTECTED] To: tutor@python.org Sent: Sunday, September 30, 2007 1:07:02 PM Subject: Re: [Tutor] CGI File Woes No doubt cgitb is a great tool for debugging cgi, but IIUC there are at least two instances when you will not get the pretty printed tracebacks in the browser when using cgitb. One is after, what I would call, a 'compile time' exception such as SyntaxError, in your python code. The other is when the python code runs without exception, but you have not separated the header and the document content with a newline. At least, I have found these to be true when using apache-cgi. Consider the following examples: #!/usr/bin/env python # raises a SyntaxError import cgi import cgitb; cgitb.enable() print Content-type: text/html\n\n # NOTE: purposeful misspelling of the print statement prin htmlbodypHello, world!/p/body/html # the code above will produce a server 500, with apache # complaining about premature end of script headers ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
