Basic CGI Applications
<![CDATA[
What is CGI?
---------------
Common Gateway Interface
Typical applications:
1) forms processing
2) gateway, (Oracle DB)
3) virtual documents
4) server side cickable maps
=> servers - might require specific directories
example:
public_html/cgi-bin
=> or file extensions
examples:
.pl <= Perl extension
.cgi
Can use:
C/C++
C shell
Perl
Tcl
VB
Java
file exists on server, html page points to file
<html>
<a href = "frame.cgi"> frame.cgi</a>
<a href = "frame.pl"> frame.pl </a>
<br>
<!-- #include virtual="frame.pl"-->
<br>
<!-- #include virtual="frame.cgi"-->
</html>
Perl Code
----------
#!/usr/local/bin/perl
print "content-type: text/html\n\n";
print "<HTML> <BODY> <H1>Hello World</H1>\n";
print "</BODY> </HTML>\n";
file for output must be:
chmod a+rwx
o+w
C++ code:
-----------
#include <iostream.h>
void main()
{
cout << "Content-type: text/plain\n\n";
cout << "Hello World\n";
}
g++ compiler doesn't work well, instead try CC, (Solaris C++ compiler)
- you MUST use .C as extension (Note: CC and .C must be in caps!)
HTML file to access a the C++ Program
-------------------------------------
please note the space following the <!-- must be removed to get these
directives to behave as includes and not simple comments
<html>
<a href="a.cgi">a.cgi</a>
<!-- #include virtual="a.cgi"-->
</html>
cgiwrap is sometimes useful on some systems
<!-- #include virtual="cgi-bin/cgiwrap/engweb/____.pl"-->
Perl Script that performs file I/O
----------------------------------
#!/usr/local/bin/perl
print "Content-type: text/html\n\n"; #indicate mime content
print "<HTML>\n";
print "<BODY>\n";
$file = 'test.dat'; #file is in html page directory
open(IN, "<$file") || die "Cannot open $file"; #open file for input
@lines = <IN>; #put the lines in an array
close(IN);
foreach $line (@lines) #process lines one at a time
{
print "<P> $line </P>\n";
}
print "</BODY>\n";
print "</HTML>\n";
$out = "results.dat"; #file is in html page directory
open(OUT,">$out") || die "Cannot open $out"; #open file for output
print OUT "Some Data Lines\n";
for ($i = 1; $i < 5; $i++)
{
print OUT "$i\n";
}
close(OUT);
C++ Version that does file I/O
------------------------------
#include <iostream.h>
#include <fstream.h>
void main()
{
ifstream in;
ofstream out;
char S[30];
int i;
in.open("test.dat"); // open input file
cout << "Content-type: text/html\n\n"; // indicate mime content
cout << "<HTML>\n";
cout << "<BODY>\n";
in >> S;
cout << "<H1>";
cout << S;
cout << "</H1>\n";
in >> i;
while (!in.eof())
{
cout << i;
cout << "<br>";
cout << "\n";
in >> i;
}
in.close();
cout << "</BODY>\n";
cout << "</HTML>\n";
out.open("results.dat"); //open output file
out << "Some Numbers\n";
for (i = 10; i < 20; i++)
{
out << i;
out << "\n";
}
out.close();
}
]]>
Server Side Includes:
--------------------
note: the space before the # needs to be removed to make these constructs
behave as directives and not html comments
<![CDATA[
<a href="a.cgi">a.cgi</a> <!-- a.cgi is a compiled c++ prog-->
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<HTML>
<BODY>
<H1>Hello World</H1>
</BODY>
</HTML>
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H L X
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]]>
<![CDATA[
<!-- #echo var="DATE_GMT"-->
]]>
Wednesday, 25-Nov-2009 12:12:22 GMT
<![CDATA[
<!-- #echo var="SERVER_NAME"-->
]]>
www.engin.umd.umich.edu
<![CDATA[
<!-- #exec cmd="cal"--> <!-- gives a default calendar for current month in Unix-->
]]>
[an error occurred while processing this directive]
<![CDATA[
<!-- #exec cmd="finger bmaxim"-->
]]>
[an error occurred while processing this directive]
<![CDATA[
<!-- #exec cmd="man unzip"--> <!-- would include all 14 unzip man pages-->
]]>
<![CDATA[
<!-- #exec cgi="a.pl"-->
]]>
[an error occurred while processing this directive]
<![CDATA[
<!-- #exec cgi="a.out"--> <!-- where a.out is a compiled c++ program-->
]]>
[an error occurred while processing this directive]
<![CDATA[
<!-- #exec cgi="a.cgi"-->
]]>
[an error occurred while processing this directive]
<![CDATA[
<!-- #config errmsg="if error occurs, contact bmaxim@umich.edu"-->
]]>
Working with Forms:
-----------------------
It is hard to find examples of form processinng using C++. This site
contains several
Perl examples of CGI programming and form processing.