Doc/lib/libcgitb.tex

   1 \section{\module{cgitb} ---
   2          Traceback manager for CGI scripts}
   3
   4 \declaremodule{standard}{cgitb}
   5 \modulesynopsis{Configurable traceback handler for CGI scripts.}
   6 \moduleauthor{Ka-Ping Yee}{ping@lfw.org}
   7 \sectionauthor{Fred L. Drake, Jr.}{fdrake@acm.org}
   8
   9 \versionadded{2.2}
  10 \index{CGI!exceptions}
  11 \index{CGI!tracebacks}
  12 \index{exceptions!in CGI scripts}
  13 \index{tracebacks!in CGI scripts}
  14
  15 The \module{cgitb} module provides a special exception handler for Python
  16 scripts.  (Its name is a bit misleading.  It was originally designed to
  17 display extensive traceback information in HTML for CGI scripts.  It was
  18 later generalized to also display this information in plain text.)  After
  19 this module is activated, if an uncaught exception occurs, a detailed,
  20 formatted report will be displayed.  The report
  21 includes a traceback showing excerpts of the source code for each level,
  22 as well as the values of the arguments and local variables to currently
  23 running functions, to help you debug the problem.  Optionally, you can
  24 save this information to a file instead of sending it to the browser.
  25
  26 To enable this feature, simply add one line to the top of your CGI script:
  27
  28 \begin{verbatim}
  29 import cgitb; cgitb.enable()
  30 \end{verbatim}
  31
  32 The options to the \function{enable()} function control whether the
  33 report is displayed in the browser and whether the report is logged
  34 to a file for later analysis.
  35
  36
  37 \begin{funcdesc}{enable}{\optional{display\optional{, logdir\optional{,
  38                          context\optional{, format}}}}}
  39   This function causes the \module{cgitb} module to take over the
  40   interpreter's default handling for exceptions by setting the
  41   value of \code{\refmodule{sys}.excepthook}.
  42   \withsubitem{(in module sys)}{\ttindex{excepthook()}}
  43
  44   The optional argument \var{display} defaults to \code{1} and can be set
  45   to \code{0} to suppress sending the traceback to the browser.
  46   If the argument \var{logdir} is present, the traceback reports are
  47   written to files.  The value of \var{logdir} should be a directory
  48   where these files will be placed.
  49   The optional argument \var{context} is the number of lines of
  50   context to display around the current line of source code in the
  51   traceback; this defaults to \code{5}.
  52   If the optional argument \var{format} is \code{"html"}, the output is
  53   formatted as HTML.  Any other value forces plain text output.  The default
  54   value is \code{"html"}.
  55 \end{funcdesc}
  56
  57 \begin{funcdesc}{handler}{\optional{info}}
  58   This function handles an exception using the default settings
  59   (that is, show a report in the browser, but don't log to a file).
  60   This can be used when you've caught an exception and want to
  61   report it using \module{cgitb}.  The optional \var{info} argument
  62   should be a 3-tuple containing an exception type, exception
  63   value, and traceback object, exactly like the tuple returned by
  64   \code{\refmodule{sys}.exc_info()}.  If the \var{info} argument
  65   is not supplied, the current exception is obtained from
  66   \code{\refmodule{sys}.exc_info()}.
  67 \end{funcdesc}