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Python Source | 2000-08-23 | 48.6 KB | 1,387 lines

#! /usr/local/bin/python """Support module for CGI (Common Gateway Interface) scripts. This module defines a number of utilities for use by CGI scripts written in Python. Introduction ------------ A CGI script is invoked by an HTTP server, usually to process user input submitted through an HTML <FORM> or <ISINPUT> element. Most often, CGI scripts live in the server's special cgi-bin directory. The HTTP server places all sorts of information about the request (such as the client's hostname, the requested URL, the query string, and lots of other goodies) in the script's shell environment, executes the script, and sends the script's output back to the client. The script's input is connected to the client too, and sometimes the form data is read this way; at other times the form data is passed via the "query string" part of the URL. This module (cgi.py) is intended to take care of the different cases and provide a simpler interface to the Python script. It also provides a number of utilities that help in debugging scripts, and the latest addition is support for file uploads from a form (if your browser supports it -- Grail 0.3 and Netscape 2.0 do). The output of a CGI script should consist of two sections, separated 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: print "Content-type: text/html" # HTML is following print # blank line, end of headers 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: print "<TITLE>CGI script output</TITLE>" print "<H1>This is my first CGI script</H1>" print "Hello, world!" It may not be fully legal HTML according to the letter of the standard, but any browser will understand it. Using the cgi module -------------------- Begin by writing "import cgi". Don't use "from cgi import *" -- the module defines all sorts of names for its own use or for backward compatibility that you don't want in your namespace. It's best to use the FieldStorage class. The other classes define in this module are provided mostly for backward compatibility. Instantiate it exactly once, without arguments. This reads the form contents from standard input or the environment (depending on the value of various environment variables set according to the CGI standard). Since it may consume standard input, it should be instantiated only once. The FieldStorage instance can be accessed as if it were a Python dictionary. For instance, the following code (which assumes that the Content-type header and blank line have already been printed) checks that the fields "name" and "addr" are both set to a non-empty string: 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... Here the fields, accessed through form[key], are themselves instances of FieldStorage (or MiniFieldStorage, depending on the form encoding). If the submitted form data contains more than one field with the same name, the object retrieved by form[key] is not a (Mini)FieldStorage instance but a list of such instances. If you are expecting this possibility (i.e., when your HTML form comtains multiple fields with the same name), use the 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: 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 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: 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 The file upload draft standard entertains the possibility of uploading multiple files from one field (using a recursive multipart/* encoding). When this occurs, the item will be a dictionary-like FieldStorage item. This can be determined by testing its type attribute, which should have the value "multipart/form-data" (or perhaps another string beginning with "multipart/"). It this case, it can be iterated over recursively just like the top-level form object. When a form is submitted in the "old" format (as the query string or as a single data part of type application/x-www-form-urlencoded), the items will actually be instances of the class MiniFieldStorage. In this case, the list, file and filename attributes are always None. Old classes ----------- These classes, present in earlier versions of the cgi module, are still supported for backward compatibility. New applications should use the FieldStorage class. SvFormContentDict: single value form content as dictionary; assumes each field name occurs in the form only once. FormContentDict: multiple value form content as dictionary (the form items are lists of values). Useful if your form contains multiple fields with the same name. Other classes (FormContent, InterpFormContentDict) are present for backwards compatibility with really old applications only. If you still use these and would be inconvenienced when they disappeared from a next version of this module, drop me a note. Functions --------- These are useful if you want more control, or if you want to employ some of the algorithms implemented in this module in other circumstances. parse(fp, [environ, [keep_blank_values, [strict_parsing]]]): parse a form into a Python dictionary. parse_qs(qs, [keep_blank_values, [strict_parsing]]): parse a query string (data of type application/x-www-form-urlencoded). Data are returned as a dictionary. The dictionary keys are the unique query variable names and the values are lists of vales for each name. parse_qsl(qs, [keep_blank_values, [strict_parsing]]): parse a query string (data of type application/x-www-form-urlencoded). Data are returned as a list of (name, value) pairs. parse_multipart(fp, pdict): parse input of type multipart/form-data (for file uploads). parse_header(string): parse a header like Content-type into a main value and a dictionary of parameters. test(): complete test program. print_environ(): format the shell environment in HTML. print_form(form): format a form in HTML. print_environ_usage(): print a list of useful environment variables in HTML. escape(): convert the characters "&", "<" and ">" to HTML-safe sequences. Use this if you need to display text that might contain such characters in HTML. To translate URLs for inclusion in the HREF attribute of an <A> tag, use urllib.quote(). log(fmt, ...): write a line to a log file; see docs for initlog(). Caring about security --------------------- There's one important rule: if you invoke an external program (e.g. via the os.system() or os.popen() functions), make very sure you don't pass arbitrary strings received from the client to the shell. This is a well-known security hole whereby clever hackers anywhere on the web can exploit a gullible CGI script to invoke arbitrary shell commands. Even parts of the URL or field names cannot be trusted, since the request doesn't have to come from your form! To be on the safe side, if you must pass a string gotten from a form to a shell command, you should make sure the string contains only alphanumeric characters, dashes, underscores, and periods. Installing your CGI script on a Unix system ------------------------------------------- Read the documentation for your HTTP server and check with your local system administrator to find the directory where CGI scripts should be installed; usually this is in a directory cgi-bin in the server tree. Make sure that your script is readable and executable by "others"; the Unix file mode should be 755 (use "chmod 755 filename"). Make sure that the first line of the script contains #! starting in column 1 followed by the pathname of the Python interpreter, for instance: #! /usr/local/bin/python Make sure the Python interpreter exists and is executable by "others". Note that it's probably not a good idea to use #! /usr/bin/env python here, since the Python interpreter may not be on the default path given to CGI scripts!!! Make sure that any files your script needs to read or write are readable or writable, respectively, by "others" -- their mode should be 644 for readable and 666 for writable. This is because, for security reasons, the HTTP server executes your script as user "nobody", without any special privileges. It can only read (write, execute) files that everybody can read (write, execute). The current directory at execution time is also different (it is usually the server's cgi-bin directory) and the set of environment variables is also different from what you get at login. in particular, don't count on the shell's search path for executables ($PATH) or the Python module search path ($PYTHONPATH) to be set to anything interesting. 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.: import sys sys.path.insert(0, "/usr/home/joe/lib/python") sys.path.insert(0, "/usr/local/lib/python") This way, the directory inserted last will be searched first! Instructions for non-Unix systems will vary; check your HTTP server's documentation (it will usually have a section on CGI scripts). Testing your CGI script ----------------------- Unfortunately, a CGI script will generally not run when you try it from the command line, and a script that works perfectly from the command line may fail mysteriously when run from the server. There's one reason why you should still test your script from the command line: if it contains a syntax error, the python interpreter won't execute it at all, and the HTTP server will most likely send a cryptic error to the client. Assuming your script has no syntax errors, yet it does not work, you have no choice but to read the next section: Debugging CGI scripts --------------------- First of all, check for trivial installation errors -- reading the section above on installing your CGI script carefully can save you a lot of time. If you wonder whether you have understood the installation procedure correctly, try installing a copy of this module file (cgi.py) as a CGI script. When invoked as a script, the file will dump its environment and the contents of the form in HTML form. Give it the right mode etc, and send it a request. If it's installed in the standard cgi-bin directory, it should be possible to send it a request by entering a URL into your browser of the form: http://yourhostname/cgi-bin/cgi.py?name=Joe+Blow&addr=At+Home 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 you should fix before trying to go any further. If you get a nicely formatted listing of the environment and form content (in this example, the fields should be listed as "addr" with value "At Home" and "name" with value "Joe Blow"), the cgi.py script has been installed correctly. If you follow the same procedure for your own script, you should now be able to debug it. The next step could be to call the cgi module's test() function from your script: replace its main code with the single statement cgi.test() This should produce the same results as those gotten from installing the cgi.py file itself. When an ordinary Python script raises an unhandled exception (e.g., because of a typo in a module name, a file that can't be opened, etc.), the Python interpreter prints a nice traceback and exits. While the Python interpreter will still do this when your CGI script raises an exception, most likely the traceback will end up in one of the HTTP server's log file, or be discarded altogether. Fortunately, once you have managed to get your script to execute *some* code, it is easy to catch exceptions and cause a traceback to be printed. The test() function below in this module is an example. Here are the rules: 1. Import the traceback module (before entering the try-except!) 2. Make sure you finish printing the headers and the blank line early 3. Assign sys.stderr to sys.stdout 3. Wrap all remaining code in a try-except statement 4. In the except clause, call traceback.print_exc() For example: 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() Notes: The assignment to sys.stderr is needed because the traceback prints to sys.stderr. The print "\n\n<PRE>" statement is necessary to disable the word wrapping in HTML. 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): import sys sys.stderr = sys.stdout print "Content-type: text/plain" print ...your code here... 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 by your client. If it raises an exception, most likely after the first two lines have been printed, a traceback will be displayed. Because no HTML interpretation is going on, the traceback will readable. When all else fails, you may want to insert calls to log() to your program or even to a copy of the cgi.py file. Note that this requires you to set cgi.logfile to the name of a world-writable file before the first call to log() is made! Good luck! 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. History ------- Michael McLay started this module. Steve Majewski changed the interface to SvFormContentDict and FormContentDict. The multipart parsing was inspired by code submitted by Andreas Paepcke. Guido van Rossum rewrote, reformatted and documented the module and is currently responsible for its maintenance. XXX The module is getting pretty heavy with all those docstrings. Perhaps there should be a slimmed version that doesn't contain all those backwards compatible and debugging classes and functions? """ __version__ = "2.2" # Imports # ======= import string import sys import os import urllib import mimetools import rfc822 from StringIO import StringIO # Logging support # =============== logfile = "" # Filename to log to, if not empty logfp = None # File object to log to, if not None def initlog(*allargs): """Write a log message, if there is a log file. Even though this function is called initlog(), you should always use log(); log is a variable that is set either to initlog (initially), to dolog (once the log file has been opened), or to nolog (when logging is disabled). The first argument is a format string; the remaining arguments (if any) are arguments to the % operator, so e.g. log("%s: %s", "a", "b") will write "a: b" to the log file, followed by a newline. If the global logfp is not None, it should be a file object to which log data is written. If the global logfp is None, the global logfile may be a string giving a filename to open, in append mode. This file should be world writable!!! If the file can't be opened, logging is silently disabled (since there is no safe place where we could send an error message). """ global logfp, log if logfile and not logfp: try: logfp = open(logfile, "a") except IOError: pass if not logfp: log = nolog else: log = dolog apply(log, allargs) def dolog(fmt, *args): """Write a log message to the log file. See initlog() for docs.""" logfp.write(fmt%args + "\n") def nolog(*allargs): """Dummy function, assigned to log when logging is disabled.""" pass log = initlog # The current logging function # Parsing functions # ================= # Maximum input we will accept when REQUEST_METHOD is POST # 0 ==> unlimited input maxlen = 0 def parse(fp=None, environ=os.environ, keep_blank_values=0, strict_parsing=0): """Parse a query in the environment or from a file (default stdin) Arguments, all optional: fp : file pointer; default: sys.stdin environ : environment dictionary; default: os.environ keep_blank_values: flag indicating whether blank values in URL encoded forms should be treated as blank strings. A true value inicates that blanks should be retained as blank strings. The default false value indicates that blank values are to be ignored and treated as if they were not included. strict_parsing: flag indicating what to do with parsing errors. If false (the default), errors are silently ignored. If true, errors raise a ValueError exception. """ if not fp: fp = sys.stdin if not environ.has_key('REQUEST_METHOD'): environ['REQUEST_METHOD'] = 'GET' # For testing stand-alone if environ['REQUEST_METHOD'] == 'POST': ctype, pdict = parse_header(environ['CONTENT_TYPE']) if ctype == 'multipart/form-data': return parse_multipart(fp, pdict) elif ctype == 'application/x-www-form-urlencoded': clength = string.atoi(environ['CONTENT_LENGTH']) if maxlen and clength > maxlen: raise ValueError, 'Maximum content length exceeded' qs = fp.read(clength) else: qs = '' # Unknown content-type if environ.has_key('QUERY_STRING'): if qs: qs = qs + '&' qs = qs + environ['QUERY_STRING'] elif sys.argv[1:]: if qs: qs = qs + '&' qs = qs + sys.argv[1] environ['QUERY_STRING'] = qs # XXX Shouldn't, really elif environ.has_key('QUERY_STRING'): qs = environ['QUERY_STRING'] else: if sys.argv[1:]: qs = sys.argv[1] else: qs = "" environ['QUERY_STRING'] = qs # XXX Shouldn't, really return parse_qs(qs, keep_blank_values, strict_parsing) def parse_qs(qs, keep_blank_values=0, strict_parsing=0): """Parse a query given as a string argument. Arguments: qs: URL-encoded query string to be parsed keep_blank_values: flag indicating whether blank values in URL encoded queries should be treated as blank strings. A true value inicates that blanks should be retained as blank strings. The default false value indicates that blank values are to be ignored and treated as if they were not included. strict_parsing: flag indicating what to do with parsing errors. If false (the default), errors are silently ignored. If true, errors raise a ValueError exception. """ dict = {} for name, value in parse_qsl(qs, keep_blank_values, strict_parsing): if len(value) or keep_blank_values: if dict.has_key(name): dict[name].append(value) else: dict[name] = [value] return dict def parse_qsl(qs, keep_blank_values=0, strict_parsing=0): """Parse a query given as a string argument. Arguments: qs: URL-encoded query string to be parsed keep_blank_values: flag indicating whether blank values in URL encoded queries should be treated as blank strings. A true value inicates that blanks should be retained as blank strings. The default false value indicates that blank values are to be ignored and treated as if they were not included. strict_parsing: flag indicating what to do with parsing errors. If false (the default), errors are silently ignored. If true, errors raise a ValueError exception. Returns a list, as God intended. """ name_value_pairs = string.splitfields(qs, '&') r=[] for name_value in name_value_pairs: nv = string.splitfields(name_value, '=') if len(nv) != 2: if strict_parsing: raise ValueError, "bad query field: %s" % `name_value` continue name = urllib.unquote(string.replace(nv[0], '+', ' ')) value = urllib.unquote(string.replace(nv[1], '+', ' ')) r.append((name, value)) return r def parse_multipart(fp, pdict): """Parse multipart input. Arguments: fp : input file pdict: dictionary containing other parameters of conten-type header Returns a dictionary just like parse_qs(): keys are the field names, each value is a list of values for that field. This is easy to use but not much good if you are expecting megabytes to be uploaded -- in that case, use the FieldStorage class instead which is much more flexible. Note that content-type is the raw, unparsed contents of the content-type header. XXX This does not parse nested multipart parts -- use FieldStorage for that. XXX This should really be subsumed by FieldStorage altogether -- no point in having two implementations of the same parsing algorithm. """ if pdict.has_key('boundary'): boundary = pdict['boundary'] else: boundary = "" nextpart = "--" + boundary lastpart = "--" + boundary + "--" partdict = {} terminator = "" while terminator != lastpart: bytes = -1 data = None if terminator: # At start of next part. Read headers first. headers = mimetools.Message(fp) clength = headers.getheader('content-length') if clength: try: bytes = string.atoi(clength) except string.atoi_error: pass if bytes > 0: if maxlen and bytes > maxlen: raise ValueError, 'Maximum content length exceeded' data = fp.read(bytes) else: data = "" # Read lines until end of part. lines = [] while 1: line = fp.readline() if not line: terminator = lastpart # End outer loop break if line[:2] == "--": terminator = string.strip(line) if terminator in (nextpart, lastpart): break lines.append(line) # Done with part. if data is None: continue if bytes < 0: if lines: # Strip final line terminator line = lines[-1] if line[-2:] == "\r\n": line = line[:-2] elif line[-1:] == "\n": line = line[:-1] lines[-1] = line data = string.joinfields(lines, "") line = headers['content-disposition'] if not line: continue key, params = parse_header(line) if key != 'form-data': continue if params.has_key('name'): name = params['name'] else: continue if partdict.has_key(name): partdict[name].append(data) else: partdict[name] = [data] return partdict def parse_header(line): """Parse a Content-type like header. Return the main content-type and a dictionary of options. """ plist = map(string.strip, string.splitfields(line, ';')) key = string.lower(plist[0]) del plist[0] pdict = {} for p in plist: i = string.find(p, '=') if i >= 0: name = string.lower(string.strip(p[:i])) value = string.strip(p[i+1:]) if len(value) >= 2 and value[0] == value[-1] == '"': value = value[1:-1] pdict[name] = value return key, pdict # Classes for field storage # ========================= class MiniFieldStorage: """Like FieldStorage, for use when no file uploads are possible.""" # Dummy attributes filename = None list = None type = None file = None type_options = {} disposition = None disposition_options = {} headers = {} def __init__(self, name, value): """Constructor from field name and value.""" self.name = name self.value = value # self.file = StringIO(value) def __repr__(self): """Return printable representation.""" return "MiniFieldStorage(%s, %s)" % (`self.name`, `self.value`) class FieldStorage: """Store a sequence of fields, reading multipart/form-data. This class provides naming, typing, files stored on disk, and more. At the top level, it is accessible like a dictionary, whose keys are the field names. (Note: None can occur as a field name.) The items are either a Python list (if there's multiple values) or another FieldStorage or MiniFieldStorage object. If it's a single object, it has the following attributes: name: the field name, if specified; otherwise None filename: the filename, if specified; otherwise None; this is the client side filename, *not* the file name on which it is stored (that's a temporary file you don't deal with) value: the value as a *string*; for file uploads, this transparently reads the file every time you request the value file: the file(-like) object from which you can read the data; None if the data is stored a simple string type: the content-type, or None if not specified type_options: dictionary of options specified on the content-type line disposition: content-disposition, or None if not specified disposition_options: dictionary of corresponding options headers: a dictionary(-like) object (sometimes rfc822.Message or a subclass thereof) containing *all* headers The class is subclassable, mostly for the purpose of overriding the make_file() method, which is called internally to come up with a file open for reading and writing. This makes it possible to override the default choice of storing all files in a temporary directory and unlinking them as soon as they have been opened. """ def __init__(self, fp=None, headers=None, outerboundary="", environ=os.environ, keep_blank_values=0, strict_parsing=0): """Constructor. Read multipart/* until last part. Arguments, all optional: fp : file pointer; default: sys.stdin (not used when the request method is GET) headers : header dictionary-like object; default: taken from environ as per CGI spec outerboundary : terminating multipart boundary (for internal use only) environ : environment dictionary; default: os.environ keep_blank_values: flag indicating whether blank values in URL encoded forms should be treated as blank strings. A true value inicates that blanks should be retained as blank strings. The default false value indicates that blank values are to be ignored and treated as if they were not included. strict_parsing: flag indicating what to do with parsing errors. If false (the default), errors are silently ignored. If true, errors raise a ValueError exception. """ method = 'GET' self.keep_blank_values = keep_blank_values self.strict_parsing = strict_parsing if environ.has_key('REQUEST_METHOD'): method = string.upper(environ['REQUEST_METHOD']) if method == 'GET' or method == 'HEAD': if environ.has_key('QUERY_STRING'): qs = environ['QUERY_STRING'] elif sys.argv[1:]: qs = sys.argv[1] else: qs = "" fp = StringIO(qs) if headers is None: headers = {'content-type': "application/x-www-form-urlencoded"} if headers is None: headers = {} if method == 'POST': # Set default content-type for POST to what's traditional headers['content-type'] = "application/x-www-form-urlencoded" if environ.has_key('CONTENT_TYPE'): headers['content-type'] = environ['CONTENT_TYPE'] if environ.has_key('CONTENT_LENGTH'): headers['content-length'] = environ['CONTENT_LENGTH'] self.fp = fp or sys.stdin self.headers = headers self.outerboundary = outerboundary # Process content-disposition header cdisp, pdict = "", {} if self.headers.has_key('content-disposition'): cdisp, pdict = parse_header(self.headers['content-disposition']) self.disposition = cdisp self.disposition_options = pdict self.name = None if pdict.has_key('name'): self.name = pdict['name'] self.filename = None if pdict.has_key('filename'): self.filename = pdict['filename'] # Process content-type header # # Honor any existing content-type header. But if there is no # content-type header, use some sensible defaults. Assume # outerboundary is "" at the outer level, but something non-false # inside a multi-part. The default for an inner part is text/plain, # but for an outer part it should be urlencoded. This should catch # bogus clients which erroneously forget to include a content-type # header. # # See below for what we do if there does exist a content-type header, # but it happens to be something we don't understand. if self.headers.has_key('content-type'): ctype, pdict = parse_header(self.headers['content-type']) elif self.outerboundary or method != 'POST': ctype, pdict = "text/plain", {} else: ctype, pdict = 'application/x-www-form-urlencoded', {} self.type = ctype self.type_options = pdict self.innerboundary = "" if pdict.has_key('boundary'): self.innerboundary = pdict['boundary'] clen = -1 if self.headers.has_key('content-length'): try: clen = string.atoi(self.headers['content-length']) except: pass if maxlen and clen > maxlen: raise ValueError, 'Maximum content length exceeded' self.length = clen self.list = self.file = None self.done = 0 self.lines = [] if ctype == 'application/x-www-form-urlencoded': self.read_urlencoded() elif ctype[:10] == 'multipart/': self.read_multi(environ, keep_blank_values, strict_parsing) else: self.read_single() def __repr__(self): """Return a printable representation.""" return "FieldStorage(%s, %s, %s)" % ( `self.name`, `self.filename`, `self.value`) def __getattr__(self, name): if name != 'value': raise AttributeError, name if self.file: self.file.seek(0) value = self.file.read() self.file.seek(0) elif self.list is not None: value = self.list else: value = None return value def __getitem__(self, key): """Dictionary style indexing.""" if self.list is None: raise TypeError, "not indexable" found = [] for item in self.list: if item.name == key: found.append(item) if not found: raise KeyError, key if len(found) == 1: return found[0] else: return found def keys(self): """Dictionary style keys() method.""" if self.list is None: raise TypeError, "not indexable" keys = [] for item in self.list: if item.name not in keys: keys.append(item.name) return keys def has_key(self, key): """Dictionary style has_key() method.""" if self.list is None: raise TypeError, "not indexable" for item in self.list: if item.name == key: return 1 return 0 def __len__(self): """Dictionary style len(x) support.""" return len(self.keys()) def read_urlencoded(self): """Internal: read data in query string format.""" qs = self.fp.read(self.length) self.list = list = [] for key, value in parse_qsl(qs, self.keep_blank_values, self.strict_parsing): list.append(MiniFieldStorage(key, value)) self.skip_lines() FieldStorageClass = None def read_multi(self, environ, keep_blank_values, strict_parsing): """Internal: read a part that is itself multipart.""" self.list = [] klass = self.FieldStorageClass or self.__class__ part = klass(self.fp, {}, self.innerboundary, environ, keep_blank_values, strict_parsing) # Throw first part away while not part.done: headers = rfc822.Message(self.fp) part = klass(self.fp, headers, self.innerboundary, environ, keep_blank_values, strict_parsing) self.list.append(part) self.skip_lines() def read_single(self): """Internal: read an atomic part.""" if self.length >= 0: self.read_binary() self.skip_lines() else: self.read_lines() self.file.seek(0) bufsize = 8*1024 # I/O buffering size for copy to file def read_binary(self): """Internal: read binary data.""" self.file = self.make_file('b') todo = self.length if todo >= 0: while todo > 0: data = self.fp.read(min(todo, self.bufsize)) if not data: self.done = -1 break self.file.write(data) todo = todo - len(data) def read_lines(self): """Internal: read lines until EOF or outerboundary.""" self.file = self.make_file('') if self.outerboundary: self.read_lines_to_outerboundary() else: self.read_lines_to_eof() def read_lines_to_eof(self): """Internal: read lines until EOF.""" while 1: line = self.fp.readline() if not line: self.done = -1 break # self.lines.append(line) self.file.write(line) def read_lines_to_outerboundary(self): """Internal: read lines until outerboundary.""" next = "--" + self.outerboundary last = next + "--" delim = "" while 1: line = self.fp.readline() if not line: self.done = -1 break # self.lines.append(line) if line[:2] == "--": strippedline = string.strip(line) if strippedline == next: break if strippedline == last: self.done = 1 break odelim = delim if line[-2:] == "\r\n": delim = "\r\n" line = line[:-2] elif line[-1] == "\n": delim = "\n" line = line[:-1] else: delim = "" self.file.write(odelim + line) def skip_lines(self): """Internal: skip lines until outer boundary if defined.""" if not self.outerboundary or self.done: return next = "--" + self.outerboundary last = next + "--" while 1: line = self.fp.readline() if not line: self.done = -1 break # self.lines.append(line) if line[:2] == "--": strippedline = string.strip(line) if strippedline == next: break if strippedline == last: self.done = 1 break def make_file(self, binary=None): """Overridable: return a readable & writable file. The file will be used as follows: - data is written to it - seek(0) - data is read from it The 'binary' argument is unused -- the file is always opened in binary mode. This version opens a temporary file for reading and writing, and immediately deletes (unlinks) it. The trick (on Unix!) is that the file can still be used, but it can't be opened by another process, and it will automatically be deleted when it is closed or when the current process terminates. If you want a more permanent file, you derive a class which overrides this method. If you want a visible temporary file that is nevertheless automatically deleted when the script terminates, try defining a __del__ method in a derived class which unlinks the temporary files you have created. """ import tempfile return tempfile.TemporaryFile("w+b") # Backwards Compatibility Classes # =============================== class FormContentDict: """Basic (multiple values per field) form content as dictionary. form = FormContentDict() form[key] -> [value, value, ...] form.has_key(key) -> Boolean form.keys() -> [key, key, ...] form.values() -> [[val, val, ...], [val, val, ...], ...] form.items() -> [(key, [val, val, ...]), (key, [val, val, ...]), ...] form.dict == {key: [val, val, ...], ...} """ def __init__(self, environ=os.environ): self.dict = parse(environ=environ) self.query_string = environ['QUERY_STRING'] def __getitem__(self,key): return self.dict[key] def keys(self): return self.dict.keys() def has_key(self, key): return self.dict.has_key(key) def values(self): return self.dict.values() def items(self): return self.dict.items() def __len__( self ): return len(self.dict) class SvFormContentDict(FormContentDict): """Strict single-value expecting form content as dictionary. IF you only expect a single value for each field, then form[key] will return that single value. It will raise an IndexError if that expectation is not true. IF you expect a field to have possible multiple values, than you can use form.getlist(key) to get all of the values. values() and items() are a compromise: they return single strings where there is a single value, and lists of strings otherwise. """ def __getitem__(self, key): if len(self.dict[key]) > 1: raise IndexError, 'expecting a single value' return self.dict[key][0] def getlist(self, key): return self.dict[key] def values(self): lis = [] for each in self.dict.values(): if len( each ) == 1 : lis.append(each[0]) else: lis.append(each) return lis def items(self): lis = [] for key,value in self.dict.items(): if len(value) == 1 : lis.append((key, value[0])) else: lis.append((key, value)) return lis class InterpFormContentDict(SvFormContentDict): """This class is present for backwards compatibility only.""" def __getitem__( self, key ): v = SvFormContentDict.__getitem__( self, key ) if v[0] in string.digits+'+-.' : try: return string.atoi( v ) except ValueError: try: return string.atof( v ) except ValueError: pass return string.strip(v) def values( self ): lis = [] for key in self.keys(): try: lis.append( self[key] ) except IndexError: lis.append( self.dict[key] ) return lis def items( self ): lis = [] for key in self.keys(): try: lis.append( (key, self[key]) ) except IndexError: lis.append( (key, self.dict[key]) ) return lis class FormContent(FormContentDict): """This class is present for backwards compatibility only.""" def values(self, key): if self.dict.has_key(key) :return self.dict[key] else: return None def indexed_value(self, key, location): if self.dict.has_key(key): if len (self.dict[key]) > location: return self.dict[key][location] else: return None else: return None def value(self, key): if self.dict.has_key(key): return self.dict[key][0] else: return None def length(self, key): return len(self.dict[key]) def stripped(self, key): if self.dict.has_key(key): return string.strip(self.dict[key][0]) else: return None def pars(self): return self.dict # Test/debug code # =============== def test(environ=os.environ): """Robust test CGI script, usable as main program. Write minimal HTTP headers and dump all information provided to the script in HTML form. """ import traceback print "Content-type: text/html" print sys.stderr = sys.stdout try: form = FieldStorage() # Replace with other classes to test those print_form(form) print_environ(environ) print_directory() print_arguments() print_environ_usage() def f(): exec "testing print_exception() -- <I>italics?</I>" def g(f=f): f() print "<H3>What follows is a test, not an actual exception:</H3>" g() except: print_exception() # Second try with a small maxlen... global maxlen maxlen = 50 try: form = FieldStorage() # Replace with other classes to test those print_form(form) print_environ(environ) print_directory() print_arguments() print_environ_usage() except: print_exception() def print_exception(type=None, value=None, tb=None, limit=None): if type is None: type, value, tb = sys.exc_info() import traceback print print "<H3>Traceback (innermost last):</H3>" list = traceback.format_tb(tb, limit) + \ traceback.format_exception_only(type, value) print "<PRE>%s<B>%s</B></PRE>" % ( escape(string.join(list[:-1], "")), escape(list[-1]), ) del tb def print_environ(environ=os.environ): """Dump the shell environment as HTML.""" keys = environ.keys() keys.sort() print print "<H3>Shell Environment:</H3>" print "<DL>" for key in keys: print "<DT>", escape(key), "<DD>", escape(environ[key]) print "</DL>" print def print_form(form): """Dump the contents of a form as HTML.""" keys = form.keys() keys.sort() print print "<H3>Form Contents:</H3>" print "<DL>" for key in keys: print "<DT>" + escape(key) + ":", value = form[key] print "<i>" + escape(`type(value)`) + "</i>" print "<DD>" + escape(`value`) print "</DL>" print def print_directory(): """Dump the current directory as HTML.""" print print "<H3>Current Working Directory:</H3>" try: pwd = os.getcwd() except os.error, msg: print "os.error:", escape(str(msg)) else: print escape(pwd) print def print_arguments(): print print "<H3>Command Line Arguments:</H3>" print print sys.argv print def print_environ_usage(): """Dump a list of environment variables used by CGI as HTML.""" print """ <H3>These environment variables could have been set:</H3> <UL> <LI>AUTH_TYPE <LI>CONTENT_LENGTH <LI>CONTENT_TYPE <LI>DATE_GMT <LI>DATE_LOCAL <LI>DOCUMENT_NAME <LI>DOCUMENT_ROOT <LI>DOCUMENT_URI <LI>GATEWAY_INTERFACE <LI>LAST_MODIFIED <LI>PATH <LI>PATH_INFO <LI>PATH_TRANSLATED <LI>QUERY_STRING <LI>REMOTE_ADDR <LI>REMOTE_HOST <LI>REMOTE_IDENT <LI>REMOTE_USER <LI>REQUEST_METHOD <LI>SCRIPT_NAME <LI>SERVER_NAME <LI>SERVER_PORT <LI>SERVER_PROTOCOL <LI>SERVER_ROOT <LI>SERVER_SOFTWARE </UL> In addition, HTTP headers sent by the server may be passed in the environment as well. Here are some common variable names: <UL> <LI>HTTP_ACCEPT <LI>HTTP_CONNECTION <LI>HTTP_HOST <LI>HTTP_PRAGMA <LI>HTTP_REFERER <LI>HTTP_USER_AGENT </UL> """ # Utilities # ========= def escape(s, quote=None): """Replace special characters '&', '<' and '>' by SGML entities.""" s = string.replace(s, "&", "&") # Must be done first! s = string.replace(s, "<", "<") s = string.replace(s, ">", ">",) if quote: s = string.replace(s, '"', """) return s # Invoke mainline # =============== # Call test() when this file is run as a script (not imported as a module) if __name__ == '__main__': test()