11.1.9 Common problems and solutions

• Most HTTP servers buffer the output from CGI scripts until the script is completed. This means that it is not possible to display a progress report on the client's display while the script is running.
• Check the installation instructions above.
• Check the HTTP server's log files. (tail -f logfile in a separate window may be useful!)
• Always check a script for syntax errors first, by doing something like python script.py.
• When using any of the debugging techniques, don't forget to add import sys to the top of the script.
• When invoking external programs, make sure they can be found. Usually, this means using absolute path names - $PATH is usually not set to a very useful value in a CGI script.
• When reading or writing external files, make sure they can be read or written by every user on the system.
• Don't try to give a CGI script a set-uid mode. This doesn't work on most systems, and is a security liability as well.