Posting to a CGI script

August 14, 2002 | Fredrik Lundh

Q. I’m looking for a general way to have a CGI script fetch the whole body of an HTTP POST request and put in a variable.

When the CGI script runs, things are set up so that you can simply read from standard input.

variable = sys.stdin.read()

To avoid denial-of-service attacks, it’s probably a good idea to limit the amount of data read by the script:

bytes = int(os.environ.get("CONTENT_LENGTH", 0))

if bytes > MAX_REQUEST_SIZE:
    giveup("request too large")

variable = sys.stdin.read(bytes)

or, simpler:

variable = sys.stdin.read(MAX_REQUEST_SIZE)

if len(variable) == MAX_REQUEST_SIZE and sys.stdin.read(1):
    giveup("request too large")

For a larger example, see Providing XML-RPC Services via CGI.