Gecko [ v99win.today ]

Name	Size	Permission
2to3.html	63.71 KB	-rw-r--r--
__builtin__.html	11.79 KB	-rw-r--r--
__future__.html	15.58 KB	-rw-r--r--
__main__.html	8.33 KB	-rw-r--r--
_winreg.html	73.99 KB	-rw-r--r--
abc.html	26.82 KB	-rw-r--r--
aepack.html	15.47 KB	-rw-r--r--
aetools.html	18.79 KB	-rw-r--r--
aetypes.html	27.08 KB	-rw-r--r--
aifc.html	29.59 KB	-rw-r--r--
al.html	22.13 KB	-rw-r--r--
allos.html	35.48 KB	-rw-r--r--
anydbm.html	19.31 KB	-rw-r--r--
archiving.html	10.64 KB	-rw-r--r--
argparse.html	269.59 KB	-rw-r--r--
array.html	35.35 KB	-rw-r--r--
ast.html	42.42 KB	-rw-r--r--
asynchat.html	35.84 KB	-rw-r--r--
asyncore.html	43.22 KB	-rw-r--r--
atexit.html	19.23 KB	-rw-r--r--
audioop.html	41.32 KB	-rw-r--r--
autogil.html	9.77 KB	-rw-r--r--
base64.html	24.8 KB	-rw-r--r--
basehttpserver.html	40.6 KB	-rw-r--r--
bastion.html	13.02 KB	-rw-r--r--
bdb.html	50.06 KB	-rw-r--r--
binascii.html	26.64 KB	-rw-r--r--
binhex.html	12.66 KB	-rw-r--r--
bisect.html	28.52 KB	-rw-r--r--
bsddb.html	32.02 KB	-rw-r--r--
bz2.html	31.92 KB	-rw-r--r--
calendar.html	50.16 KB	-rw-r--r--
carbon.html	54.14 KB	-rw-r--r--
cd.html	35.24 KB	-rw-r--r--
cgi.html	58.4 KB	-rw-r--r--
cgihttpserver.html	15.12 KB	-rw-r--r--
cgitb.html	13.5 KB	-rw-r--r--
chunk.html	17.41 KB	-rw-r--r--
cmath.html	32.41 KB	-rw-r--r--
cmd.html	32.69 KB	-rw-r--r--
code.html	28.92 KB	-rw-r--r--
codecs.html	125.92 KB	-rw-r--r--
codeop.html	16.42 KB	-rw-r--r--
collections.html	150.36 KB	-rw-r--r--
colorpicker.html	9.02 KB	-rw-r--r--
colorsys.html	14.38 KB	-rw-r--r--
commands.html	16.63 KB	-rw-r--r--
compileall.html	21.18 KB	-rw-r--r--
compiler.html	78.14 KB	-rw-r--r--
configparser.html	73.92 KB	-rw-r--r--
constants.html	14.68 KB	-rw-r--r--
contextlib.html	22.91 KB	-rw-r--r--
cookie.html	45.38 KB	-rw-r--r--
cookielib.html	102.78 KB	-rw-r--r--
copy.html	14.21 KB	-rw-r--r--
copy_reg.html	15.82 KB	-rw-r--r--
crypt.html	11.62 KB	-rw-r--r--
crypto.html	8.35 KB	-rw-r--r--
csv.html	82.79 KB	-rw-r--r--
ctypes.html	280.57 KB	-rw-r--r--
curses.ascii.html	28.97 KB	-rw-r--r--
curses.html	200.94 KB	-rw-r--r--
curses.panel.html	18.43 KB	-rw-r--r--
custominterp.html	8.59 KB	-rw-r--r--
datatypes.html	18.84 KB	-rw-r--r--
datetime.html	261.02 KB	-rw-r--r--
dbhash.html	18.4 KB	-rw-r--r--
dbm.html	14.75 KB	-rw-r--r--
debug.html	11.28 KB	-rw-r--r--
decimal.html	239.14 KB	-rw-r--r--
development.html	15.27 KB	-rw-r--r--
difflib.html	96.93 KB	-rw-r--r--
dircache.html	13.66 KB	-rw-r--r--
dis.html	96.52 KB	-rw-r--r--
distribution.html	8.27 KB	-rw-r--r--
distutils.html	10.97 KB	-rw-r--r--
dl.html	19.27 KB	-rw-r--r--
doctest.html	193.18 KB	-rw-r--r--
docxmlrpcserver.html	20.02 KB	-rw-r--r--
dumbdbm.html	16.74 KB	-rw-r--r--
dummy_thread.html	11.04 KB	-rw-r--r--
dummy_threading.html	9.96 KB	-rw-r--r--
easydialogs.html	38.83 KB	-rw-r--r--
email-examples.html	47.2 KB	-rw-r--r--
email.charset.html	32.45 KB	-rw-r--r--
email.encoders.html	14.09 KB	-rw-r--r--
email.errors.html	19.2 KB	-rw-r--r--
email.generator.html	24.78 KB	-rw-r--r--
email.header.html	31.12 KB	-rw-r--r--
email.html	55.3 KB	-rw-r--r--
email.iterators.html	14.22 KB	-rw-r--r--
email.message.html	74.91 KB	-rw-r--r--
email.mime.html	34.51 KB	-rw-r--r--
email.parser.html	37.09 KB	-rw-r--r--
email.utils.html	30.04 KB	-rw-r--r--
ensurepip.html	20.21 KB	-rw-r--r--
errno.html	52.31 KB	-rw-r--r--
exceptions.html	73.4 KB	-rw-r--r--
fcntl.html	27.85 KB	-rw-r--r--
filecmp.html	26.49 KB	-rw-r--r--
fileformats.html	10.21 KB	-rw-r--r--
fileinput.html	29.36 KB	-rw-r--r--
filesys.html	11.55 KB	-rw-r--r--
fl.html	71.58 KB	-rw-r--r--
fm.html	15 KB	-rw-r--r--
fnmatch.html	17.78 KB	-rw-r--r--
formatter.html	43.91 KB	-rw-r--r--
fpectl.html	17.84 KB	-rw-r--r--
fpformat.html	12.65 KB	-rw-r--r--
fractions.html	27.17 KB	-rw-r--r--
framework.html	44.24 KB	-rw-r--r--
frameworks.html	8.11 KB	-rw-r--r--
ftplib.html	56.56 KB	-rw-r--r--
functions.html	216.84 KB	-rw-r--r--
functools.html	31.06 KB	-rw-r--r--
future_builtins.html	15.9 KB	-rw-r--r--
gc.html	30.74 KB	-rw-r--r--
gdbm.html	19.35 KB	-rw-r--r--
gensuitemodule.html	14.54 KB	-rw-r--r--
getopt.html	26.56 KB	-rw-r--r--
getpass.html	12.5 KB	-rw-r--r--
gettext.html	91.32 KB	-rw-r--r--
gl.html	26.71 KB	-rw-r--r--
glob.html	15.42 KB	-rw-r--r--
grp.html	12.33 KB	-rw-r--r--
gzip.html	21.95 KB	-rw-r--r--
hashlib.html	27.4 KB	-rw-r--r--
heapq.html	36.72 KB	-rw-r--r--
hmac.html	15.97 KB	-rw-r--r--
hotshot.html	22.69 KB	-rw-r--r--
htmllib.html	29.9 KB	-rw-r--r--
htmlparser.html	45.11 KB	-rw-r--r--
httplib.html	78.55 KB	-rw-r--r--
i18n.html	10.61 KB	-rw-r--r--
ic.html	22.03 KB	-rw-r--r--
idle.html	45.74 KB	-rw-r--r--
imageop.html	20.94 KB	-rw-r--r--
imaplib.html	69.9 KB	-rw-r--r--
imgfile.html	14.91 KB	-rw-r--r--
imghdr.html	13.43 KB	-rw-r--r--
imp.html	41.48 KB	-rw-r--r--
importlib.html	10.27 KB	-rw-r--r--
imputil.html	36.11 KB	-rw-r--r--
index.html	82.54 KB	-rw-r--r--
inspect.html	64.31 KB	-rw-r--r--
internet.html	26.77 KB	-rw-r--r--
intro.html	9.76 KB	-rw-r--r--
io.html	122.3 KB	-rw-r--r--
ipc.html	17.18 KB	-rw-r--r--
itertools.html	129.91 KB	-rw-r--r--
jpeg.html	15.36 KB	-rw-r--r--
json.html	79.09 KB	-rw-r--r--
keyword.html	9.27 KB	-rw-r--r--
language.html	12.35 KB	-rw-r--r--
linecache.html	12.7 KB	-rw-r--r--
locale.html	68.54 KB	-rw-r--r--
logging.config.html	82.23 KB	-rw-r--r--
logging.handlers.html	91.96 KB	-rw-r--r--
logging.html	123.15 KB	-rw-r--r--
mac.html	24.49 KB	-rw-r--r--
macos.html	18.51 KB	-rw-r--r--
macosa.html	14.55 KB	-rw-r--r--
macostools.html	19.67 KB	-rw-r--r--
macpath.html	9.19 KB	-rw-r--r--
mailbox.html	185.53 KB	-rw-r--r--
mailcap.html	15.3 KB	-rw-r--r--
markup.html	20.37 KB	-rw-r--r--
marshal.html	19.88 KB	-rw-r--r--
math.html	50.52 KB	-rw-r--r--
md5.html	16.65 KB	-rw-r--r--
mhlib.html	30.04 KB	-rw-r--r--
mimetools.html	23.84 KB	-rw-r--r--
mimetypes.html	35.82 KB	-rw-r--r--
mimewriter.html	18.19 KB	-rw-r--r--
mimify.html	16.96 KB	-rw-r--r--
miniaeframe.html	14.5 KB	-rw-r--r--
misc.html	7.77 KB	-rw-r--r--
mm.html	10.19 KB	-rw-r--r--
mmap.html	33.52 KB	-rw-r--r--
modulefinder.html	19.85 KB	-rw-r--r--
modules.html	9.68 KB	-rw-r--r--
msilib.html	72.78 KB	-rw-r--r--
msvcrt.html	24.1 KB	-rw-r--r--
multifile.html	28.82 KB	-rw-r--r--
multiprocessing.html	423.97 KB	-rw-r--r--
mutex.html	13.56 KB	-rw-r--r--
netdata.html	19.28 KB	-rw-r--r--
netrc.html	15.51 KB	-rw-r--r--
new.html	16.1 KB	-rw-r--r--
nis.html	13.19 KB	-rw-r--r--
nntplib.html	51.08 KB	-rw-r--r--
numbers.html	40.91 KB	-rw-r--r--
numeric.html	14.85 KB	-rw-r--r--
operator.html	118.32 KB	-rw-r--r--
optparse.html	251.08 KB	-rw-r--r--
os.html	270.49 KB	-rw-r--r--
os.path.html	48.87 KB	-rw-r--r--
ossaudiodev.html	49.79 KB	-rw-r--r--
othergui.html	9.98 KB	-rw-r--r--
parser.html	44.52 KB	-rw-r--r--
pdb.html	41.44 KB	-rw-r--r--
persistence.html	16.25 KB	-rw-r--r--
pickle.html	107.94 KB	-rw-r--r--
pickletools.html	13.21 KB	-rw-r--r--
pipes.html	21.85 KB	-rw-r--r--
pkgutil.html	30.59 KB	-rw-r--r--
platform.html	40.14 KB	-rw-r--r--
plistlib.html	20.96 KB	-rw-r--r--
popen2.html	30.13 KB	-rw-r--r--
poplib.html	27.93 KB	-rw-r--r--
posix.html	17.27 KB	-rw-r--r--
posixfile.html	23.68 KB	-rw-r--r--
pprint.html	36.42 KB	-rw-r--r--
profile.html	76.65 KB	-rw-r--r--
pty.html	11.42 KB	-rw-r--r--
pwd.html	13.53 KB	-rw-r--r--
py_compile.html	13.33 KB	-rw-r--r--
pyclbr.html	18.14 KB	-rw-r--r--
pydoc.html	14.33 KB	-rw-r--r--
pyexpat.html	93.28 KB	-rw-r--r--
python.html	13.53 KB	-rw-r--r--
queue.html	29.64 KB	-rw-r--r--
quopri.html	14.5 KB	-rw-r--r--
random.html	47.78 KB	-rw-r--r--
re.html	163.11 KB	-rw-r--r--
readline.html	41.2 KB	-rw-r--r--
repr.html	24.57 KB	-rw-r--r--
resource.html	30.86 KB	-rw-r--r--
restricted.html	12.69 KB	-rw-r--r--
rexec.html	43.59 KB	-rw-r--r--
rfc822.html	51.25 KB	-rw-r--r--
rlcompleter.html	15.29 KB	-rw-r--r--
robotparser.html	15.01 KB	-rw-r--r--
runpy.html	23.55 KB	-rw-r--r--
sched.html	21.76 KB	-rw-r--r--
scrolledtext.html	10.67 KB	-rw-r--r--
select.html	50.17 KB	-rw-r--r--
sets.html	39.92 KB	-rw-r--r--
sgi.html	11.09 KB	-rw-r--r--
sgmllib.html	38.77 KB	-rw-r--r--
sha.html	14.55 KB	-rw-r--r--
shelve.html	32.93 KB	-rw-r--r--
shlex.html	38.43 KB	-rw-r--r--
shutil.html	49.49 KB	-rw-r--r--
signal.html	36.52 KB	-rw-r--r--
simplehttpserver.html	21.57 KB	-rw-r--r--
simplexmlrpcserver.html	40.41 KB	-rw-r--r--
site.html	29 KB	-rw-r--r--
smtpd.html	15.64 KB	-rw-r--r--
smtplib.html	51.86 KB	-rw-r--r--
sndhdr.html	12.05 KB	-rw-r--r--
socket.html	126.94 KB	-rw-r--r--
socketserver.html	81.38 KB	-rw-r--r--
someos.html	17.09 KB	-rw-r--r--
spwd.html	12.25 KB	-rw-r--r--
sqlite3.html	154.12 KB	-rw-r--r--
ssl.html	214.5 KB	-rw-r--r--
stat.html	41.11 KB	-rw-r--r--
statvfs.html	13.24 KB	-rw-r--r--
stdtypes.html	309.83 KB	-rw-r--r--
string.html	129.58 KB	-rw-r--r--
stringio.html	21.1 KB	-rw-r--r--
stringprep.html	21.4 KB	-rw-r--r--
strings.html	16.42 KB	-rw-r--r--
struct.html	47.68 KB	-rw-r--r--
subprocess.html	117 KB	-rw-r--r--
sun.html	7.83 KB	-rw-r--r--
sunau.html	35.43 KB	-rw-r--r--
sunaudio.html	21.05 KB	-rw-r--r--
symbol.html	9.06 KB	-rw-r--r--
symtable.html	29.03 KB	-rw-r--r--
sys.html	118.12 KB	-rw-r--r--
sysconfig.html	28.8 KB	-rw-r--r--
syslog.html	21.29 KB	-rw-r--r--
tabnanny.html	12.78 KB	-rw-r--r--
tarfile.html	99.54 KB	-rw-r--r--
telnetlib.html	30.46 KB	-rw-r--r--
tempfile.html	35.02 KB	-rw-r--r--
termios.html	19.22 KB	-rw-r--r--
test.html	61.42 KB	-rw-r--r--
textwrap.html	32.28 KB	-rw-r--r--
thread.html	22.67 KB	-rw-r--r--
threading.html	92.04 KB	-rw-r--r--
time.html	65.55 KB	-rw-r--r--
timeit.html	44.38 KB	-rw-r--r--
tix.html	56.73 KB	-rw-r--r--
tk.html	26.76 KB	-rw-r--r--
tkinter.html	86.67 KB	-rw-r--r--
token.html	27.31 KB	-rw-r--r--
tokenize.html	21.69 KB	-rw-r--r--
trace.html	33.91 KB	-rw-r--r--
traceback.html	44.22 KB	-rw-r--r--
ttk.html	123.83 KB	-rw-r--r--
tty.html	10.95 KB	-rw-r--r--
turtle.html	246.17 KB	-rw-r--r--
types.html	33.66 KB	-rw-r--r--
undoc.html	25.54 KB	-rw-r--r--
unicodedata.html	22.64 KB	-rw-r--r--
unittest.html	246.75 KB	-rw-r--r--
unix.html	11.9 KB	-rw-r--r--
urllib.html	71.61 KB	-rw-r--r--
urllib2.html	128.77 KB	-rw-r--r--
urlparse.html	49.04 KB	-rw-r--r--
user.html	13.41 KB	-rw-r--r--
userdict.html	32.96 KB	-rw-r--r--
uu.html	13.25 KB	-rw-r--r--
uuid.html	33.55 KB	-rw-r--r--
warnings.html	51.86 KB	-rw-r--r--
wave.html	29.08 KB	-rw-r--r--
weakref.html	41.14 KB	-rw-r--r--
webbrowser.html	29.53 KB	-rw-r--r--
whichdb.html	10.44 KB	-rw-r--r--
windows.html	10.37 KB	-rw-r--r--
winsound.html	22.56 KB	-rw-r--r--
wsgiref.html	94.38 KB	-rw-r--r--
xdrlib.html	38.05 KB	-rw-r--r--
xml.dom.html	110.39 KB	-rw-r--r--
xml.dom.minidom.html	45.23 KB	-rw-r--r--
xml.dom.pulldom.html	16.32 KB	-rw-r--r--
xml.etree.elementtree.html	124.2 KB	-rw-r--r--
xml.html	18.76 KB	-rw-r--r--
xml.sax.handler.html	47.5 KB	-rw-r--r--
xml.sax.html	26.04 KB	-rw-r--r--
xml.sax.reader.html	51.4 KB	-rw-r--r--
xml.sax.utils.html	18.11 KB	-rw-r--r--
xmlrpclib.html	71.79 KB	-rw-r--r--
zipfile.html	67.26 KB	-rw-r--r--
zipimport.html	24.32 KB	-rw-r--r--
zlib.html	34.41 KB	-rw-r--r--

Code Editor : cgi.html

<!DOCTYPE html>

<title>20.2. cgi — Common Gateway Interface support &#8212; Python 2.7.18 documentation</title>
 <link rel="stylesheet" type="text/css" href="../_static/pygments.css" />
 <link rel="stylesheet" type="text/css" href="../_static/classic.css" />
 
 <script data-url_root="../" id="documentation_options" src="../_static/documentation_options.js"></script>
 <script src="../_static/jquery.js"></script>
 <script src="../_static/underscore.js"></script>
 <script src="../_static/doctools.js"></script>
 
 <script src="../_static/sidebar.js"></script>
 
 <link rel="search" type="application/opensearchdescription+xml"
 title="Search within Python 2.7.18 documentation"
 href="../_static/opensearch.xml"/>
 <link rel="author" title="About these documents" href="../about.html" />
 <link rel="index" title="Index" href="../genindex.html" />
 <link rel="search" title="Search" href="../search.html" />
 <link rel="copyright" title="Copyright" href="../copyright.html" />
 <link rel="next" title="20.3. cgitb — Traceback manager for CGI scripts" href="cgitb.html" />
 <link rel="prev" title="20.1. webbrowser — Convenient Web-browser controller" href="webbrowser.html" />
 <link rel="shortcut icon" type="image/png" href="../_static/py.png" />
 <link rel="canonical" href="file:///usr/share/doc/python2.7/html/library/cgi.html" />
 <script type="text/javascript" src="../_static/copybutton.js"></script>

</head><body>
<div id="outdated-warning" style="padding: .5em; text-align: center; background-color: #FFBABA; color: #6A0E0E;">
 This document is for an old version of Python that is <a href="https://devguide.python.org/devcycle/#end-of-life-branches">no longer supported</a>.
 You should install the python3 and python3-doc packages and read the 
 <a href="file:///usr/share/doc/python3-doc/html/library/cgi.html"> Python documentation for the Python3 version packaged in this release</a>.
</div>
 
 <div class="related" role="navigation" aria-label="related navigation">
 <h3>Navigation</h3>
 <ul>
 <li class="right" style="margin-right: 10px">
 <a href="../genindex.html" title="General Index"
 accesskey="I">index</a></li>
 <li class="right" >
 <a href="../py-modindex.html" title="Python Module Index"
 >modules</a> |</li>
 <li class="right" >
 <a href="cgitb.html" title="20.3. cgitb — Traceback manager for CGI scripts"
 accesskey="N">next</a> |</li>
 <li class="right" >
 <a href="webbrowser.html" title="20.1. webbrowser — Convenient Web-browser controller"
 accesskey="P">previous</a> |</li>
 <li><img src="../_static/py.png" alt=""
 style="vertical-align: middle; margin-top: -1px"/></li>
 <li><a href="https://www.python.org/">Python</a> &#187;</li>
 <li>
 <a href="../index.html">Python 2.7.18 documentation</a> &#187;
 </li>

<li class="nav-item nav-item-1"><a href="index.html" >The Python Standard Library</a> &#187;</li>
 <li class="nav-item nav-item-2"><a href="internet.html" accesskey="U">20. Internet Protocols and Support</a> &#187;</li>
 <li class="nav-item nav-item-this"><a href="">20.2. <code class="xref py py-mod docutils literal notranslate">cgi</code> — Common Gateway Interface support</a></li> 
 </ul>
 </div>

<div class="document">
 <div class="documentwrapper">
 <div class="bodywrapper">
 <div class="body" role="main">
 
 <section id="module-cgi">
<h1>20.2. <a class="reference internal" href="#module-cgi" title="cgi: Helpers for running Python scripts via the Common Gateway Interface."><code class="xref py py-mod docutils literal notranslate">cgi</code></a> — Common Gateway Interface support<a class="headerlink" href="#module-cgi" title="Permalink to this headline">¶</a></h1>
Source code: <a class="reference external" href="https://github.com/python/cpython/tree/2.7/Lib/cgi.py">Lib/cgi.py</a>
<hr class="docutils" />
Support module for Common Gateway Interface (CGI) scripts.
This module defines a number of utilities for use by CGI scripts written in
Python.
<section id="introduction">
<h2>20.2.1. Introduction<a class="headerlink" href="#introduction" title="Permalink to this headline">¶</a></h2>
A CGI script is invoked by an HTTP server, usually to process user input
submitted through an HTML <code class="docutils literal notranslate">&lt;FORM&gt;</code> or <code class="docutils literal notranslate">&lt;ISINDEX&gt;</code> element.
Most often, CGI scripts live in the server’s special <code class="file docutils literal notranslate">cgi-bin</code> 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 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).
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:
<div class="highlight-default notranslate"><div class="highlight"><pre>print &quot;Content-Type: text/html&quot; # HTML is following
print # blank line, end of headers
</pre></div>
</div>
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:
<div class="highlight-default notranslate"><div class="highlight"><pre>print &quot;&lt;TITLE&gt;CGI script output&lt;/TITLE&gt;&quot;
print &quot;&lt;H1&gt;This is my first CGI script&lt;/H1&gt;&quot;
print &quot;Hello, world!&quot;
</pre></div>
</div>
</section>
<section id="using-the-cgi-module">
<h2>20.2.2. Using the cgi module<a class="headerlink" href="#using-the-cgi-module" title="Permalink to this headline">¶</a></h2>
Begin by writing <code class="docutils literal notranslate">import cgi</code>. Do not use <code class="docutils literal notranslate">from cgi import *</code> — the
module defines all sorts of names for its own use or for backward compatibility
that you don’t want in your namespace.
When you write a new script, consider adding these lines:
<div class="highlight-default notranslate"><div class="highlight"><pre>import cgitb
cgitb.enable()
</pre></div>
</div>
This activates a special exception handler that will display detailed reports in
the Web browser if any errors occur. If you’d rather not show the guts of your
program to users of your script, you can have the reports saved to files
instead, with code like this:
<div class="highlight-default notranslate"><div class="highlight"><pre>import cgitb
cgitb.enable(display=0, logdir=&quot;/path/to/logdir&quot;)
</pre></div>
</div>
It’s very helpful to use this feature during script development. The reports
produced by <a class="reference internal" href="cgitb.html#module-cgitb" title="cgitb: Configurable traceback handler for CGI scripts."><code class="xref py py-mod docutils literal notranslate">cgitb</code></a> provide information that can save you a lot of time in
tracking down bugs. You can always remove the <code class="docutils literal notranslate">cgitb</code> line later when you
have tested your script and are confident that it works correctly.
To get at submitted form data, it’s best to use the <code class="xref py py-class docutils literal notranslate">FieldStorage</code> class.
The other classes defined 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 <code class="xref py py-class docutils literal notranslate">FieldStorage</code> instance can be indexed like a Python dictionary.
It allows membership testing with the <a class="reference internal" href="../reference/expressions.html#in"><code class="xref std std-keyword docutils literal notranslate">in</code></a> operator, and also supports
the standard dictionary method <a class="reference internal" href="stdtypes.html#dict.keys" title="dict.keys"><code class="xref py py-meth docutils literal notranslate">keys()</code></a> and the built-in function
<a class="reference internal" href="functions.html#len" title="len"><code class="xref py py-func docutils literal notranslate">len()</code></a>. Form fields containing empty strings are ignored and do not appear
in the dictionary; to keep such values, provide a true value for the optional
keep_blank_values keyword parameter when creating the <code class="xref py py-class docutils literal notranslate">FieldStorage</code>
instance.
For instance, the following code (which assumes that the
Content-Type header and blank line have already been printed)
checks that the fields <code class="docutils literal notranslate">name</code> and <code class="docutils literal notranslate">addr</code> are both set to a non-empty
string:
<div class="highlight-default notranslate"><div class="highlight"><pre>form = cgi.FieldStorage()
if &quot;name&quot; not in form or &quot;addr&quot; not in form:
 print &quot;&lt;H1&gt;Error&lt;/H1&gt;&quot;
 print &quot;Please fill in the name and addr fields.&quot;
 return
print &quot;&lt;p&gt;name:&quot;, form[&quot;name&quot;].value
print &quot;&lt;p&gt;addr:&quot;, form[&quot;addr&quot;].value
...further form processing here...
</pre></div>
</div>
Here the fields, accessed through <code class="docutils literal notranslate">form[key]</code>, are themselves instances of
<code class="xref py py-class docutils literal notranslate">FieldStorage</code> (or <code class="xref py py-class docutils literal notranslate">MiniFieldStorage</code>, depending on the form
encoding). The <code class="xref py py-attr docutils literal notranslate">value</code> attribute of the instance yields
the string value of the field. The <code class="xref py py-meth docutils literal notranslate">getvalue()</code> method
returns this string value directly; it also accepts an optional second argument
as a default to return if the requested key is not present.
If the submitted form data contains more than one field with the same name, the
object retrieved by <code class="docutils literal notranslate">form[key]</code> is not a <code class="xref py py-class docutils literal notranslate">FieldStorage</code> or
<code class="xref py py-class docutils literal notranslate">MiniFieldStorage</code> instance but a list of such instances. Similarly, in
this situation, <code class="docutils literal notranslate">form.getvalue(key)</code> would return a list of strings. If you
expect this possibility (when your HTML form contains multiple fields with the
same name), use the <a class="reference internal" href="#cgi.FieldStorage.getlist" title="cgi.FieldStorage.getlist"><code class="xref py py-meth docutils literal notranslate">getlist()</code></a> method, which always returns
a list of values (so that you do not need to special-case the single item
case). For example, this code concatenates any number of username fields,
separated by commas:
<div class="highlight-default notranslate"><div class="highlight"><pre>value = form.getlist(&quot;username&quot;)
usernames = &quot;,&quot;.join(value)
</pre></div>
</div>
If a field represents an uploaded file, accessing the value via the
<code class="xref py py-attr docutils literal notranslate">value</code> attribute or the <code class="xref py py-func docutils literal notranslate">getvalue()</code>
method 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
<code class="xref py py-attr docutils literal notranslate">filename</code> attribute or the <code class="xref py py-attr docutils literal notranslate">file</code>
attribute. You can then read the data at leisure from the <code class="xref py py-attr docutils literal notranslate">file</code>
attribute:
<div class="highlight-default notranslate"><div class="highlight"><pre>fileitem = form[&quot;userfile&quot;]
if fileitem.file:
 # It&#39;s an uploaded file; count lines
 linecount = 0
 while 1:
 line = fileitem.file.readline()
 if not line: break
 linecount = linecount + 1
</pre></div>
</div>
If an error is encountered when obtaining the contents of an uploaded file
(for example, when the user interrupts the form submission by clicking on
a Back or Cancel button) the <code class="xref py py-attr docutils literal notranslate">done</code> attribute of the
object for the field will be set to the value -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 <code class="xref py py-class docutils literal notranslate">FieldStorage</code> item.
This can be determined by testing its <code class="xref py py-attr docutils literal notranslate">type</code> attribute, which should be
multipart/form-data (or perhaps another MIME type matching
multipart/*). In 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 <code class="xref py py-class docutils literal notranslate">MiniFieldStorage</code>. In this case, the
<code class="xref py py-attr docutils literal notranslate">list</code>, <code class="xref py py-attr docutils literal notranslate">file</code>, and <code class="xref py py-attr docutils literal notranslate">filename</code> attributes are always <code class="docutils literal notranslate">None</code>.
A form submitted via POST that also has a query string will contain both
<code class="xref py py-class docutils literal notranslate">FieldStorage</code> and <code class="xref py py-class docutils literal notranslate">MiniFieldStorage</code> items.
</section>
<section id="higher-level-interface">
<h2>20.2.3. Higher Level Interface<a class="headerlink" href="#higher-level-interface" title="Permalink to this headline">¶</a></h2>
<div class="versionadded">
New in version 2.2.
</div>
The previous section explains how to read CGI form data using the
<code class="xref py py-class docutils literal notranslate">FieldStorage</code> class. This section describes a higher level interface
which was added to this class to allow one to do it in a more readable and
intuitive way. The interface doesn’t make the techniques described in previous
sections obsolete — they are still useful to process file uploads efficiently,
for example.
The interface consists of two simple methods. Using the methods you can process
form data in a generic way, without the need to worry whether only one or more
values were posted under one name.
In the previous section, you learned to write following code anytime you
expected a user to post more than one value under one name:
<div class="highlight-default notranslate"><div class="highlight"><pre>item = form.getvalue(&quot;item&quot;)
if isinstance(item, list):
 # The user is requesting more than one item.
else:
 # The user is requesting only one item.
</pre></div>
</div>
This situation is common for example when a form contains a group of multiple
checkboxes with the same name:
<div class="highlight-default notranslate"><div class="highlight"><pre>&lt;input type=&quot;checkbox&quot; name=&quot;item&quot; value=&quot;1&quot; /&gt;
&lt;input type=&quot;checkbox&quot; name=&quot;item&quot; value=&quot;2&quot; /&gt;
</pre></div>
</div>
In most situations, however, there’s only one form control with a particular
name in a form and then you expect and need only one value associated with this
name. So you write a script containing for example this code:
<div class="highlight-default notranslate"><div class="highlight"><pre>user = form.getvalue(&quot;user&quot;).upper()
</pre></div>
</div>
The problem with the code is that you should never expect that a client will
provide valid input to your scripts. For example, if a curious user appends
another <code class="docutils literal notranslate">user=foo</code> pair to the query string, then the script would crash,
because in this situation the <code class="docutils literal notranslate">getvalue(&quot;user&quot;)</code> method call returns a list
instead of a string. Calling the <a class="reference internal" href="stdtypes.html#str.upper" title="str.upper"><code class="xref py py-meth docutils literal notranslate">upper()</code></a> method on a list is not valid
(since lists do not have a method of this name) and results in an
<code class="xref py py-exc docutils literal notranslate">AttributeError</code> exception.
Therefore, the appropriate way to read form data values was to always use the
code which checks whether the obtained value is a single value or a list of
values. That’s annoying and leads to less readable scripts.
A more convenient approach is to use the methods <a class="reference internal" href="#cgi.FieldStorage.getfirst" title="cgi.FieldStorage.getfirst"><code class="xref py py-meth docutils literal notranslate">getfirst()</code></a>
and <a class="reference internal" href="#cgi.FieldStorage.getlist" title="cgi.FieldStorage.getlist"><code class="xref py py-meth docutils literal notranslate">getlist()</code></a> provided by this higher level interface.
<dl class="py method">
<dt class="sig sig-object py" id="cgi.FieldStorage.getfirst">
FieldStorage.getfirst(name[, default])<a class="headerlink" href="#cgi.FieldStorage.getfirst" title="Permalink to this definition">¶</a></dt>
<dd>This method always returns only one value associated with form field name.
The method returns only the first value in case that more values were posted
under such name. Please note that the order in which the values are received
may vary from browser to browser and should not be counted on. <a class="footnote-reference brackets" href="#id3" id="id2">1</a> If no such
form field or value exists then the method returns the value specified by the
optional parameter default. This parameter defaults to <code class="docutils literal notranslate">None</code> if not
specified.
</dd></dl>

<dl class="py method">
<dt class="sig sig-object py" id="cgi.FieldStorage.getlist">
FieldStorage.getlist(name)<a class="headerlink" href="#cgi.FieldStorage.getlist" title="Permalink to this definition">¶</a></dt>
<dd>This method always returns a list of values associated with form field name.
The method returns an empty list if no such form field or value exists for
name. It returns a list consisting of one item if only one such value exists.
</dd></dl>

Using these methods you can write nice compact code:
<div class="highlight-default notranslate"><div class="highlight"><pre>import cgi
form = cgi.FieldStorage()
user = form.getfirst(&quot;user&quot;, &quot;&quot;).upper() # This way it&#39;s safe.
for item in form.getlist(&quot;item&quot;):
 do_something(item)
</pre></div>
</div>
</section>
<section id="old-classes">
<h2>20.2.4. Old classes<a class="headerlink" href="#old-classes" title="Permalink to this headline">¶</a></h2>
<div class="deprecated">
Deprecated since version 2.6: These classes, present in earlier versions of the <a class="reference internal" href="#module-cgi" title="cgi: Helpers for running Python scripts via the Common Gateway Interface."><code class="xref py py-mod docutils literal notranslate">cgi</code></a> module, are
still supported for backward compatibility. New applications should use the
<code class="xref py py-class docutils literal notranslate">FieldStorage</code> class.
</div>
<code class="xref py py-class docutils literal notranslate">SvFormContentDict</code> stores single value form content as dictionary; it
assumes each field name occurs in the form only once.
<code class="xref py py-class docutils literal notranslate">FormContentDict</code> stores multiple value form content as a dictionary (the
form items are lists of values). Useful if your form contains multiple fields
with the same name.
Other classes (<code class="xref py py-class docutils literal notranslate">FormContent</code>, <code class="xref py py-class docutils literal notranslate">InterpFormContentDict</code>) are present
for backwards compatibility with really old applications only.
</section>
<section id="functions">
<h2>20.2.5. Functions<a class="headerlink" href="#functions" title="Permalink to this headline">¶</a></h2>
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.
<dl class="py function">
<dt class="sig sig-object py" id="cgi.parse">
cgi.parse(fp[, environ[, keep_blank_values[, strict_parsing]]])<a class="headerlink" href="#cgi.parse" title="Permalink to this definition">¶</a></dt>
<dd>Parse a query in the environment or from a file (the file defaults to
<code class="docutils literal notranslate">sys.stdin</code> and environment defaults to <code class="docutils literal notranslate">os.environ</code>). The keep_blank_values and strict_parsing parameters are
passed to <a class="reference internal" href="urlparse.html#urlparse.parse_qs" title="urlparse.parse_qs"><code class="xref py py-func docutils literal notranslate">urlparse.parse_qs()</code></a> unchanged.
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="cgi.parse_qs">
cgi.parse_qs(qs[, keep_blank_values[, strict_parsing[, max_num_fields]]])<a class="headerlink" href="#cgi.parse_qs" title="Permalink to this definition">¶</a></dt>
<dd>This function is deprecated in this module. Use <a class="reference internal" href="urlparse.html#urlparse.parse_qs" title="urlparse.parse_qs"><code class="xref py py-func docutils literal notranslate">urlparse.parse_qs()</code></a>
instead. It is maintained here only for backward compatibility.
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="cgi.parse_qsl">
cgi.parse_qsl(qs[, keep_blank_values[, strict_parsing[, max_num_fields]]])<a class="headerlink" href="#cgi.parse_qsl" title="Permalink to this definition">¶</a></dt>
<dd>This function is deprecated in this module. Use <a class="reference internal" href="urlparse.html#urlparse.parse_qsl" title="urlparse.parse_qsl"><code class="xref py py-func docutils literal notranslate">urlparse.parse_qsl()</code></a>
instead. It is maintained here only for backward compatibility.
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="cgi.parse_multipart">
cgi.parse_multipart(fp, pdict)<a class="headerlink" href="#cgi.parse_multipart" title="Permalink to this definition">¶</a></dt>
<dd>Parse input of type multipart/form-data (for file uploads).
Arguments are fp for the input file and pdict for a dictionary containing
other parameters in the Content-Type header.
Returns a dictionary just like <a class="reference internal" href="urlparse.html#urlparse.parse_qs" title="urlparse.parse_qs"><code class="xref py py-func docutils literal notranslate">urlparse.parse_qs()</code></a> 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
<code class="xref py py-class docutils literal notranslate">FieldStorage</code> class instead which is much more flexible.
Note that this does not parse nested multipart parts — use
<code class="xref py py-class docutils literal notranslate">FieldStorage</code> for that.
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="cgi.parse_header">
cgi.parse_header(string)<a class="headerlink" href="#cgi.parse_header" title="Permalink to this definition">¶</a></dt>
<dd>Parse a MIME header (such as Content-Type) into a main value and a
dictionary of parameters.
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="cgi.test">
cgi.test()<a class="headerlink" href="#cgi.test" title="Permalink to this definition">¶</a></dt>
<dd>Robust test CGI script, usable as main program. Writes minimal HTTP headers and
formats all information provided to the script in HTML form.
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="cgi.print_environ">
cgi.print_environ()<a class="headerlink" href="#cgi.print_environ" title="Permalink to this definition">¶</a></dt>
<dd>Format the shell environment in HTML.
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="cgi.print_form">
cgi.print_form(form)<a class="headerlink" href="#cgi.print_form" title="Permalink to this definition">¶</a></dt>
<dd>Format a form in HTML.
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="cgi.print_directory">
cgi.print_directory()<a class="headerlink" href="#cgi.print_directory" title="Permalink to this definition">¶</a></dt>
<dd>Format the current directory in HTML.
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="cgi.print_environ_usage">
cgi.print_environ_usage()<a class="headerlink" href="#cgi.print_environ_usage" title="Permalink to this definition">¶</a></dt>
<dd>Print a list of useful (used by CGI) environment variables in HTML.
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="cgi.escape">
cgi.escape(s[, quote])<a class="headerlink" href="#cgi.escape" title="Permalink to this definition">¶</a></dt>
<dd>Convert the characters <code class="docutils literal notranslate">'&amp;'</code>, <code class="docutils literal notranslate">'&lt;'</code> and <code class="docutils literal notranslate">'&gt;'</code> in string s to HTML-safe
sequences. Use this if you need to display text that might contain such
characters in HTML. If the optional flag quote is true, the quotation mark
character (<code class="docutils literal notranslate">&quot;</code>) is also translated; this helps for inclusion in an HTML
attribute value delimited by double quotes, as in <code class="docutils literal notranslate">&lt;a href=&quot;...&quot;&gt;</code>. Note
that single quotes are never translated.
If the value to be quoted might include single- or double-quote characters,
or both, consider using the <a class="reference internal" href="xml.sax.utils.html#xml.sax.saxutils.quoteattr" title="xml.sax.saxutils.quoteattr"><code class="xref py py-func docutils literal notranslate">quoteattr()</code></a> function in the
<a class="reference internal" href="xml.sax.utils.html#module-xml.sax.saxutils" title="xml.sax.saxutils: Convenience functions and classes for use with SAX."><code class="xref py py-mod docutils literal notranslate">xml.sax.saxutils</code></a> module instead.
</dd></dl>

</section>
<section id="caring-about-security">
<h2>20.2.6. Caring about security<a class="headerlink" href="#caring-about-security" title="Permalink to this headline">¶</a></h2>
There’s one important rule: if you invoke an external program (via the
<a class="reference internal" href="os.html#os.system" title="os.system"><code class="xref py py-func docutils literal notranslate">os.system()</code></a> or <a class="reference internal" href="os.html#os.popen" title="os.popen"><code class="xref py py-func docutils literal notranslate">os.popen()</code></a> functions. or others with similar
functionality), 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.
</section>
<section id="installing-your-cgi-script-on-a-unix-system">
<h2>20.2.7. Installing your CGI script on a Unix system<a class="headerlink" href="#installing-your-cgi-script-on-a-unix-system" title="Permalink to this headline">¶</a></h2>
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 <code class="file docutils literal notranslate">cgi-bin</code> in the server tree.
Make sure that your script is readable and executable by “others”; the Unix file
mode should be <code class="docutils literal notranslate">0755</code> octal (use <code class="docutils literal notranslate">chmod 0755 filename</code>). Make sure that the
first line of the script contains <code class="docutils literal notranslate">#!</code> starting in column 1 followed by the
pathname of the Python interpreter, for instance:
<div class="highlight-default notranslate"><div class="highlight"><pre>#!/usr/local/bin/python
</pre></div>
</div>
Make sure the Python interpreter exists and is executable by “others”.
Make sure that any files your script needs to read or write are readable or
writable, respectively, by “others” — their mode should be <code class="docutils literal notranslate">0644</code> for
readable and <code class="docutils literal notranslate">0666</code> 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 when you log in. In particular, don’t count
on the shell’s search path for executables (<code class="xref std std-envvar docutils literal notranslate">PATH</code>) or the Python module
search path (<a class="reference internal" href="../using/cmdline.html#envvar-PYTHONPATH"><code class="xref std std-envvar docutils literal notranslate">PYTHONPATH</code></a>) 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. For example:
<div class="highlight-default notranslate"><div class="highlight"><pre>import sys
sys.path.insert(0, &quot;/usr/home/joe/lib/python&quot;)
sys.path.insert(0, &quot;/usr/local/lib/python&quot;)
</pre></div>
</div>
(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).
</section>
<section id="testing-your-cgi-script">
<h2>20.2.8. Testing your CGI script<a class="headerlink" href="#testing-your-cgi-script" title="Permalink to this headline">¶</a></h2>
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.
</section>
<section id="debugging-cgi-scripts">
<h2>20.2.9. Debugging CGI scripts<a class="headerlink" href="#debugging-cgi-scripts" title="Permalink to this headline">¶</a></h2>
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 (<code class="file docutils literal notranslate">cgi.py</code>) 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 <code class="file docutils literal notranslate">cgi-bin</code> directory, it should be possible to
send it a request by entering a URL into your browser of the form:
<div class="highlight-none notranslate"><div class="highlight"><pre>http://yourhostname/cgi-bin/cgi.py?name=Joe+Blow&amp;addr=At+Home
</pre></div>
</div>
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,
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 <code class="file docutils literal notranslate">cgi.py</code> 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 <a class="reference internal" href="#module-cgi" title="cgi: Helpers for running Python scripts via the Common Gateway Interface."><code class="xref py py-mod docutils literal notranslate">cgi</code></a> module’s <a class="reference internal" href="test.html#module-test" title="test: Regression tests package containing the testing suite for Python."><code class="xref py py-func docutils literal notranslate">test()</code></a> function
from your script: replace its main code with the single statement
<div class="highlight-default notranslate"><div class="highlight"><pre>cgi.test()
</pre></div>
</div>
This should produce the same results as those gotten from installing the
<code class="file docutils literal notranslate">cgi.py</code> file itself.
When an ordinary Python script raises an unhandled exception (for whatever
reason: 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 files, or be
discarded altogether.
Fortunately, once you have managed to get your script to execute some code,
you can easily send tracebacks to the Web browser using the <a class="reference internal" href="cgitb.html#module-cgitb" title="cgitb: Configurable traceback handler for CGI scripts."><code class="xref py py-mod docutils literal notranslate">cgitb</code></a> module.
If you haven’t done so already, just add the lines:
<div class="highlight-default notranslate"><div class="highlight"><pre>import cgitb
cgitb.enable()
</pre></div>
</div>
to the top of your script. Then try running it again; when a problem occurs,
you should see a detailed report that will likely make apparent the cause of the
crash.
If you suspect that there may be a problem in importing the <a class="reference internal" href="cgitb.html#module-cgitb" title="cgitb: Configurable traceback handler for CGI scripts."><code class="xref py py-mod docutils literal notranslate">cgitb</code></a> module,
you can use an even more robust approach (which only uses built-in modules):
<div class="highlight-default notranslate"><div class="highlight"><pre>import sys
sys.stderr = sys.stdout
print &quot;Content-Type: text/plain&quot;
print
...your code here...
</pre></div>
</div>
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 be readable.
</section>
<section id="common-problems-and-solutions">
<h2>20.2.10. Common problems and solutions<a class="headerlink" href="#common-problems-and-solutions" title="Permalink to this headline">¶</a></h2>
<ul class="simple">
<li>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.</li>
<li>Check the installation instructions above.</li>
<li>Check the HTTP server’s log files. (<code class="docutils literal notranslate">tail -f logfile</code> in a separate window
may be useful!)</li>
<li>Always check a script for syntax errors first, by doing something like
<code class="docutils literal notranslate">python script.py</code>.</li>
<li>If your script does not have any syntax errors, try adding <code class="docutils literal notranslate">import cgitb;
cgitb.enable()</code> to the top of the script.</li>
<li>When invoking external programs, make sure they can be found. Usually, this
means using absolute path names — <code class="xref std std-envvar docutils literal notranslate">PATH</code> is usually not set to a very
useful value in a CGI script.</li>
<li>When reading or writing external files, make sure they can be read or written
by the userid under which your CGI script will be running: this is typically the
userid under which the web server is running, or some explicitly specified
userid for a web server’s <code class="docutils literal notranslate">suexec</code> feature.</li>
<li>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.</li>
</ul>
Footnotes
<dl class="footnote brackets">
<dt class="label" id="id3"><a class="fn-backref" href="#id2">1</a></dt>
<dd>Note that some recent versions of the HTML specification do state what order the
field values should be supplied in, but knowing whether a request was
received from a conforming browser, or even from a browser at all, is tedious
and error-prone.
</dd>
</dl>
</section>
</section>

<div class="clearer"></div>
 </div>
 </div>
 </div>
 <div class="sphinxsidebar" role="navigation" aria-label="main navigation">
 <div class="sphinxsidebarwrapper">
 <h3><a href="../contents.html">Table of Contents</a></h3>
 <ul>
<li><a class="reference internal" href="#">20.2. <code class="xref py py-mod docutils literal notranslate">cgi</code> — Common Gateway Interface support</a><ul>
<li><a class="reference internal" href="#introduction">20.2.1. Introduction</a></li>
<li><a class="reference internal" href="#using-the-cgi-module">20.2.2. Using the cgi module</a></li>
<li><a class="reference internal" href="#higher-level-interface">20.2.3. Higher Level Interface</a></li>
<li><a class="reference internal" href="#old-classes">20.2.4. Old classes</a></li>
<li><a class="reference internal" href="#functions">20.2.5. Functions</a></li>
<li><a class="reference internal" href="#caring-about-security">20.2.6. Caring about security</a></li>
<li><a class="reference internal" href="#installing-your-cgi-script-on-a-unix-system">20.2.7. Installing your CGI script on a Unix system</a></li>
<li><a class="reference internal" href="#testing-your-cgi-script">20.2.8. Testing your CGI script</a></li>
<li><a class="reference internal" href="#debugging-cgi-scripts">20.2.9. Debugging CGI scripts</a></li>
<li><a class="reference internal" href="#common-problems-and-solutions">20.2.10. Common problems and solutions</a></li>
</ul>
</li>
</ul>

<h4>Previous topic</h4>
 <a href="webbrowser.html"
 title="previous chapter">20.1. <code class="xref py py-mod docutils literal notranslate">webbrowser</code> — Convenient Web-browser controller</a>
 <h4>Next topic</h4>
 <a href="cgitb.html"
 title="next chapter">20.3. <code class="xref py py-mod docutils literal notranslate">cgitb</code> — Traceback manager for CGI scripts</a>
 <div role="note" aria-label="source link">
 <h3>This Page</h3>
 <ul class="this-page-menu">
 <li><a href="../_sources/library/cgi.rst.txt"
 rel="nofollow">Show Source</a></li>
 </ul>
 </div>
<div id="searchbox" style="display: none" role="search">
 <h3 id="searchlabel">Quick search</h3>
 <div class="searchformwrapper">
 <form class="search" action="../search.html" method="get">
 <input type="text" name="q" aria-labelledby="searchlabel" autocomplete="off" autocorrect="off" autocapitalize="off" spellcheck="false"/>
 <input type="submit" value="Go" />
 </form>
 </div>
</div>
<script>$('#searchbox').show(0);</script>
 </div>
 </div>
 <div class="clearer"></div>
 </div> 
 <div class="related" role="navigation" aria-label="related navigation">
 <h3>Navigation</h3>
 <ul>
 <li class="right" style="margin-right: 10px">
 <a href="../genindex.html" title="General Index"
 >index</a></li>
 <li class="right" >
 <a href="../py-modindex.html" title="Python Module Index"
 >modules</a> |</li>
 <li class="right" >
 <a href="cgitb.html" title="20.3. cgitb — Traceback manager for CGI scripts"
 >next</a> |</li>
 <li class="right" >
 <a href="webbrowser.html" title="20.1. webbrowser — Convenient Web-browser controller"
 >previous</a> |</li>
 <li><img src="../_static/py.png" alt=""
 style="vertical-align: middle; margin-top: -1px"/></li>
 <li><a href="https://www.python.org/">Python</a> &#187;</li>
 <li>
 <a href="../index.html">Python 2.7.18 documentation</a> &#187;
 </li>

<li class="nav-item nav-item-1"><a href="index.html" >The Python Standard Library</a> &#187;</li>
 <li class="nav-item nav-item-2"><a href="internet.html" >20. Internet Protocols and Support</a> &#187;</li>
 <li class="nav-item nav-item-this"><a href="">20.2. <code class="xref py py-mod docutils literal notranslate">cgi</code> — Common Gateway Interface support</a></li> 
 </ul>
 </div> 
 <div class="footer">
 &copy; <a href="../copyright.html">Copyright</a> 1990-2024, Python Software Foundation.
 
 The Python Software Foundation is a non-profit corporation.
 <a href="https://www.python.org/psf/donations/">Please donate.</a>
 
 Last updated on December 09, 2024.
 <a href="../bugs.html">Found a bug</a>?
 
 Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 4.3.2.
 </div>

</body>
</html>

${this.title}

Code Editor : cgi.html