pdf file can't be opened in web service using subprocess.Popen

Question

I have a problem with opening PDF file.

(i am using Ladon and Python under mod_wsgi working with Apache2. so on a ubuntu apache server system- switched to windows system)

I'm trying to run the following Python script:

(where, str_pdf_file_name = '/var/www/Accounting_Engine/pdfDocuments/File_name.pdf')

def preview_pdf(self,str_pdf_file_name):
    try:
                if sys.version_info[:2] > (2,3):
                    import subprocess
                    from subprocess import Popen, PIPE
                    k = subprocess.Popen(['evince', str_pdf_file_name],stdout=PIPE)
                    print k.communicate()
                else:
                    os.spawnlp(os.P_NOWAIT, 'evince', 'evince', str_pdf_file_name)
    except Exception,msg:
        return str(msg)
    return str_pdf_file_name

I have disabled the stdin and stdout restrictions in apache2.conf file as

WSGIRestrictStdin Off    
WSGIRestrictStdout Off

and now the error.log file shows (/var/log/apache2/error.log):

Cannot parse arguments: Cannot open display: [Wed Oct 10 11:50:24 2012] [error] ('', None)

I have checked os.environ also. It shows like:

{'LANG': 'C', 'APACHE_RUN_USER': 'www-data', 'APACHE_PID_FILE': '/var/run/apache2.pid', 'PWD': '/home/user', 'APACHE_RUN_GROUP': 'www-data', 'PATH': '/usr/local/bin:/usr/bin:/bin'}

I have also tried by changing the PWD by using the following codes:

import pwd
os.environ["PWD"] = pwd.getpwuid(os.getuid()).pw_dir    # Because PWD of 'www-data' was '/var/www'
k = subprocess.Popen(['evince', str_pdf_file_name],env=os.environ,stdout=PIPE)

But their is no change in output. It still shows

'Cannot parse arguments: Cannot open display:'

Any suggestions what could be the cause and how to solve this?

Answer 1

#   Fetch the pdf file from the server,  and keep it in the local matchine
    str_loc_file_path = self.fetch_generated_pdf_file_from_server(str_file_path)

#   Display the fetched file in local matchine
    self.print_pdf(str_loc_file_path)

def fetch_generated_pdf_file_from_server(self, str_file_path,*args):
    import httplib
    import urllib
    conn = httplib.HTTPConnection("192.168.2.10")
    str_loc_file_path = '/home/sreejith/pdfDocuments/__filenew__.pdf'
    locfile = open(str_loc_file_path,'w')
    conn.request("POST",str_file_path)
    response = conn.getresponse()
    locfile.write(response.read())
    locfile.close()
    print "Server Response status is"+str(response.status)+", Because of response "+str(response.reason)
    print response.getheaders()    
    return str_loc_file_path

def print_pdf(self,str_file_name,*args):     # PRINT THE PDF FILE, str_file_name.
    try:
        if sys.platform == "win32":      # IS OS == WINDOWS
            import win32api          # PRINT WITH ADOBE VIEWER. SO IT MUST BE INSTALLED
            win32api.ShellExecute(0, "print", str_file_name, None, ".", 0)
        else:                # CAN'T PRINT IF OS IS LINUX, SO OPEN BY A VIEWER FROM WHICH HE CAN PRINT
            if sys.version_info[:2] > (2,3):
                import subprocess
                from subprocess import PIPE
                k = subprocess.Popen(['evince', str_file_name],stdout=PIPE)
                k.communicate()

            else:
                k = os.spawnlp(os.P_NOWAIT, 'evince', 'evince', str_file_name)
    except Exception,msg:
        print str(msg)
        msgDlg = gtk.MessageDialog(None, gtk.DIALOG_MODAL, gtk.MESSAGE_ERROR, gtk.BUTTONS_OK)
        msgDlg.set_markup("<span foreground='blue'>Printer Is Not Connected. And "+str(msg)+".</span>")
        msgDlg.run()
        msgDlg.destroy()      
    pass

This works for me. :-) Hopes helpful for somebody.