diff options
Diffstat (limited to 'Doc/libcgi.tex')
| -rw-r--r-- | Doc/libcgi.tex | 183 |
1 files changed, 92 insertions, 91 deletions
diff --git a/Doc/libcgi.tex b/Doc/libcgi.tex index 4768f0f..56643d0 100644 --- a/Doc/libcgi.tex +++ b/Doc/libcgi.tex @@ -1,4 +1,5 @@ \section{Standard Module \sectcode{cgi}} +\label{module-cgi} \stmodindex{cgi} \indexii{WWW}{server} \indexii{CGI}{protocol} @@ -39,21 +40,21 @@ by a blank line. The first section contains a number of headers, telling the client what kind of data is following. Python code to generate a minimal header section looks like this: -\begin{verbatim} - print "Content-type: text/html" # HTML is following - print # blank line, end of headers -\end{verbatim} - +\bcode\begin{verbatim} +print "Content-type: text/html" # HTML is following +print # blank line, end of headers +\end{verbatim}\ecode +% The second section is usually HTML, which allows the client software to display nicely formatted text with header, in-line images, etc. Here's Python code that prints a simple piece of HTML: -\begin{verbatim} - print "<TITLE>CGI script output</TITLE>" - print "<H1>This is my first CGI script</H1>" - print "Hello, world!" -\end{verbatim} - +\bcode\begin{verbatim} +print "<TITLE>CGI script output</TITLE>" +print "<H1>This is my first CGI script</H1>" +print "Hello, world!" +\end{verbatim}\ecode +% (It may not be fully legal HTML according to the letter of the standard, but any browser will understand it.) @@ -76,19 +77,19 @@ dictionary. For instance, the following code (which assumes that the \code{Content-type} header and blank line have already been printed) checks that the fields \code{name} and \code{addr} are both set to a non-empty string: -\begin{verbatim} - form = cgi.FieldStorage() - form_ok = 0 - if form.has_key("name") and form.has_key("addr"): - if form["name"].value != "" and form["addr"].value != "": - form_ok = 1 - if not form_ok: - print "<H1>Error</H1>" - print "Please fill in the name and addr fields." - return - ...further form processing here... -\end{verbatim} - +\bcode\begin{verbatim} +form = cgi.FieldStorage() +form_ok = 0 +if form.has_key("name") and form.has_key("addr"): + if form["name"].value != "" and form["addr"].value != "": + form_ok = 1 +if not form_ok: + print "<H1>Error</H1>" + print "Please fill in the name and addr fields." + return +...further form processing here... +\end{verbatim}\ecode +% Here the fields, accessed through \code{form[key]}, are themselves instances of \code{FieldStorage} (or \code{MiniFieldStorage}, depending on the form encoding). @@ -100,40 +101,40 @@ name), use the \code{type()} function to determine whether you have a single instance or a list of instances. For example, here's code that concatenates any number of username fields, separated by commas: -\begin{verbatim} - username = form["username"] - if type(username) is type([]): - # Multiple username fields specified - usernames = "" - for item in username: - if usernames: - # Next item -- insert comma - usernames = usernames + "," + item.value - else: - # First item -- don't insert comma - usernames = item.value - else: - # Single username field specified - usernames = username.value -\end{verbatim} - +\bcode\begin{verbatim} +username = form["username"] +if type(username) is type([]): + # Multiple username fields specified + usernames = "" + for item in username: + if usernames: + # Next item -- insert comma + usernames = usernames + "," + item.value + else: + # First item -- don't insert comma + usernames = item.value +else: + # Single username field specified + usernames = username.value +\end{verbatim}\ecode +% If a field represents an uploaded file, the value attribute reads the entire file in memory as a string. This may not be what you want. You can test for an uploaded file by testing either the filename attribute or the file attribute. You can then read the data at leasure from the file attribute: -\begin{verbatim} - fileitem = form["userfile"] - if fileitem.file: - # It's an uploaded file; count lines - linecount = 0 - while 1: - line = fileitem.file.readline() - if not line: break - linecount = linecount + 1 -\end{verbatim} - +\bcode\begin{verbatim} +fileitem = form["userfile"] +if fileitem.file: + # It's an uploaded file; count lines + linecount = 0 + while 1: + line = fileitem.file.readline() + if not line: break + linecount = linecount + 1 +\end{verbatim}\ecode +% The file upload draft standard entertains the possibility of uploading multiple files from one field (using a recursive \code{multipart/*} encoding). When this occurs, the item will be a dictionary-like @@ -251,10 +252,10 @@ Unix file mode should be 755 (use \code{chmod 755 filename}). Make sure that the first line of the script contains \code{\#!} starting in column 1 followed by the pathname of the Python interpreter, for instance: -\begin{verbatim} - #!/usr/local/bin/python -\end{verbatim} - +\bcode\begin{verbatim} +#!/usr/local/bin/python +\end{verbatim}\ecode +% Make sure the Python interpreter exists and is executable by ``others''. Make sure that any files your script needs to read or write are @@ -273,12 +274,12 @@ If you need to load modules from a directory which is not on Python's default module search path, you can change the path in your script, before importing other modules, e.g.: -\begin{verbatim} - import sys - sys.path.insert(0, "/usr/home/joe/lib/python") - sys.path.insert(0, "/usr/local/lib/python") -\end{verbatim} - +\bcode\begin{verbatim} +import sys +sys.path.insert(0, "/usr/home/joe/lib/python") +sys.path.insert(0, "/usr/local/lib/python") +\end{verbatim}\ecode +% (This way, the directory inserted last will be searched first!) Instructions for non-Unix systems will vary; check your HTTP server's @@ -311,10 +312,10 @@ Give it the right mode etc, and send it a request. If it's installed in the standard \code{cgi-bin} directory, it should be possible to send it a request by entering a URL into your browser of the form: -\begin{verbatim} - http://yourhostname/cgi-bin/cgi.py?name=Joe+Blow&addr=At+Home -\end{verbatim} - +\bcode\begin{verbatim} +http://yourhostname/cgi-bin/cgi.py?name=Joe+Blow&addr=At+Home +\end{verbatim}\ecode +% If this gives an error of type 404, the server cannot find the script -- perhaps you need to install it in a different directory. If it gives another error (e.g. 500), there's an installation problem that @@ -328,10 +329,10 @@ script, you should now be able to debug it. The next step could be to call the \code{cgi} module's test() function from your script: replace its main code with the single statement -\begin{verbatim} - cgi.test() -\end{verbatim} - +\bcode\begin{verbatim} +cgi.test() +\end{verbatim}\ecode +% This should produce the same results as those gotten from installing the \code{cgi.py} file itself. @@ -363,19 +364,19 @@ Here are the rules: For example: -\begin{verbatim} - import sys - import traceback - print "Content-type: text/html" - print - sys.stderr = sys.stdout - try: - ...your code here... - except: - print "\n\n<PRE>" - traceback.print_exc() -\end{verbatim} - +\bcode\begin{verbatim} +import sys +import traceback +print "Content-type: text/html" +print +sys.stderr = sys.stdout +try: + ...your code here... +except: + print "\n\n<PRE>" + traceback.print_exc() +\end{verbatim}\ecode +% Notes: The assignment to \code{sys.stderr} is needed because the traceback prints to \code{sys.stderr}. The \code{print "$\backslash$n$\backslash$n<PRE>"} statement is necessary to disable the word wrapping in HTML. @@ -384,14 +385,14 @@ If you suspect that there may be a problem in importing the traceback module, you can use an even more robust approach (which only uses built-in modules): -\begin{verbatim} - import sys - sys.stderr = sys.stdout - print "Content-type: text/plain" - print - ...your code here... -\end{verbatim} - +\bcode\begin{verbatim} +import sys +sys.stderr = sys.stdout +print "Content-type: text/plain" +print +...your code here... +\end{verbatim}\ecode +% This relies on the Python interpreter to print the traceback. The content type of the output is set to plain text, which disables all HTML processing. If your script works, the raw HTML will be displayed |