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| 54 | <H2><A NAME="SECTION00132100000000000000000"> |
| 55 | 11.2.10 Common problems and solutions</A> |
| 56 | </H2> |
| 57 | |
| 58 | <P> |
| 59 | |
| 60 | <UL> |
| 61 | <LI>Most HTTP servers buffer the output from CGI scripts until the |
| 62 | script is completed. This means that it is not possible to display a |
| 63 | progress report on the client's display while the script is running. |
| 64 | |
| 65 | <P> |
| 66 | </LI> |
| 67 | <LI>Check the installation instructions above. |
| 68 | |
| 69 | <P> |
| 70 | </LI> |
| 71 | <LI>Check the HTTP server's log files. ("<tt class="samp">tail -f logfile</tt>" in a |
| 72 | separate window may be useful!) |
| 73 | |
| 74 | <P> |
| 75 | </LI> |
| 76 | <LI>Always check a script for syntax errors first, by doing something |
| 77 | like "<tt class="samp">python script.py</tt>". |
| 78 | |
| 79 | <P> |
| 80 | </LI> |
| 81 | <LI>If your script does not have any syntax errors, try adding |
| 82 | "<tt class="samp">import cgitb; cgitb.enable()</tt>" to the top of the script. |
| 83 | |
| 84 | <P> |
| 85 | </LI> |
| 86 | <LI>When invoking external programs, make sure they can be found. |
| 87 | Usually, this means using absolute path names -- <a class="envvar" id='l2h-3176' xml:id='l2h-3176'>PATH</a> is |
| 88 | usually not set to a very useful value in a CGI script. |
| 89 | |
| 90 | <P> |
| 91 | </LI> |
| 92 | <LI>When reading or writing external files, make sure they can be read |
| 93 | or written by the userid under which your CGI script will be running: |
| 94 | this is typically the userid under which the web server is running, or some |
| 95 | explicitly specified userid for a web server's "<tt class="samp">suexec</tt>" feature. |
| 96 | |
| 97 | <P> |
| 98 | </LI> |
| 99 | <LI>Don't try to give a CGI script a set-uid mode. This doesn't work on |
| 100 | most systems, and is a security liability as well. |
| 101 | </LI> |
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