Run a C Program on a Linux Server
This question I'm sure has been answered, I honestly don't know how to ask it via search though. So please excuse my lack of knowledge as this one of the only place I really have a lack of knowledge in the world of Computer Science.
How can I/ Is it possible, to run a C program on a Hosted Server. To where I could go to http://mysite.com/myspecialcprogram.c and it would run? Or better yet, to what extent can I use a high level language like C to program for my server?
It should also be noted that I have a Dedicated Linux box running apache. So I have full access.
Answer
One way is to run it as CGI, as @paddy already mentioned. However, the program will run slow, long startup time.
Another way is to run it using FastCGI. It will be much more faster, you just need a few modifications on your code to make it works, for example as CGI:
#include <stdio.h>
#include <time.h>
int main(int argc, char **argv)
{
time_t timer;
char time_str[25];
struct tm* tm_info;
time(&timer);
tm_info = localtime(&timer);
strftime(time_str, sizeof(time_str), "%Y/%m/%d %H:%M:%S", tm_info);
/* Without this line, you will get 500 error */
puts("Content-type: text/html\n");
puts("<!DOCTYPE html>");
puts("<head>");
puts(" <meta charset=\"utf-8\">");
puts("</head>");
puts("<body>");
puts(" <h3>Hello world!</h3>");
printf(" <p>%s</p>\n", time_str);
puts("</body>");
puts("</html>");
return 0;
}
Compile it:
$ # 'cgi-bin' path may be different than yours
$ sudo gcc example.c -o /usr/lib/cgi-bin/example
$ wget -q -O - http://localhost/cgi-bin/example
<!DOCTYPE html>
<head>
<meta charset="utf-8">
</head>
<body>
<h3>Hello world!</h3>
<p>2013/01/30 08:07:29</p>
</body>
</html>
$
Using FastCGI:
#include <fcgi_stdio.h>
#include <stdio.h>
#include <time.h>
int main(int argc, char **argv)
{
time_t timer;
char time_str[25];
struct tm* tm_info;
while(FCGI_Accept() >= 0) {
time(&timer);
tm_info = localtime(&timer);
strftime(time_str, sizeof(time_str), "%Y/%m/%d %H:%M:%S", tm_info);
/* Without this line, you will get 500 error */
puts("Content-type: text/html\n");
puts("<!DOCTYPE html>");
puts("<head>");
puts(" <meta charset=\"utf-8\">");
puts("</head>");
puts("<body>");
puts(" <h3>Hello world!</h3>");
printf(" <p>%s</p>\n", time_str);
puts("</body>");
puts("</html>");
}
return 0;
}
Compile it:
$ # Install the development fastcgi package, I'm running Debian
$ sudo apt-get install libfcgi-dev
...
$
$ # Install Apache mod_fcgid (not mod_fastcgi)
$ sudo apt-get install libapache2-mod-fcgid
...
$
$ # Compile the fastcgi version with .fcgi extension
$ sudo gcc example.c -lfcgi -o /usr/lib/cgi-bin/example.fcgi
$ # Restart Apache
$ sudo /etc/init.d/apache2 restart
Restarting web server: apache2 ... waiting .
$
$ # You will notice how fast it is
$ wget -q -O - http://localhost/cgi-bin/example.fcgi
<!DOCTYPE html>
<head>
<meta charset="utf-8">
</head>
<body>
<h3>Hello world!</h3>
<p>2013/01/30 08:15:23</p>
</body>
</html>
$
$ # Our fastcgi script process
$ ps aux | grep \.fcgi
www-data 2552 0.0 0.1 1900 668 ? S 08:15 0:00 /usr/lib/cgi-bin/example.fcgi
$
In poth programes, there is:
puts("Content-type: text/html\n");
This will prints:
Content-type: text/html[new line]
[new line]
Without it Apache will throw 500 server internal error.