[burt@davis ~/temp]$ more getpagesize.c 

#include<stdio.h>
#include<unistd.h>

int main(int argc, char * argv[]) {
        int i ;
        printf("pagesize: %d\n", getpagesize()) ;
        printf("pointerfize: %d\n", sizeof(&i)) ;


}



[burt@davis ~/temp]$ uname -a
Linux davis.cs.miami.edu 2.6.18-1.2798.fc6 #1 SMP Mon Oct 16 14:54:20 EDT 2006 i686 athlon i386 GNU/Linux

[burt@davis ~/temp]$ ./a.out
pagesize: 4096
pointerfize: 4


[burt@davis ~/temp]$ ssh shiloh
Last login: Wed Oct  8 11:46:59 2008 from davis.cs.miami.edu

[burt@shiloh ~]$ cd temp
[burt@shiloh ~/temp]$ cc getpagesize.c 
[burt@shiloh ~/temp]$ ./a.out
pagesize: 4096
pointerfize: 8
[burt@shiloh ~/temp]$ 

[burt@shiloh ~/temp]$ uname -a
Linux shiloh.cs.miami.edu 2.6.18-53.1.19.el5 #1 SMP Tue Apr 22 03:01:10 EDT 2008 x86_64 x86_64 x86_64 GNU/Linux
[burt@shiloh ~/temp]$ 

NOTE YOU HAVE TO RECOMPILE ON 64 bits!