|GETPAGESIZE(2)||Linux Programmer's Manual||GETPAGESIZE(2)|
Since glibc 2.20: _DEFAULT_SOURCE || ! (_POSIX_C_SOURCE >= 200112L) Glibc 2.12 to 2.19: _BSD_SOURCE || ! (_POSIX_C_SOURCE >= 200112L) Before glibc 2.12: _BSD_SOURCE || _XOPEN_SOURCE >= 500
#include <unistd.h> long sz = sysconf(_SC_PAGESIZE);
(Most systems allow the synonym _SC_PAGE_SIZE for _SC_PAGESIZE.)
Whether getpagesize() is present as a Linux system call depends on the architecture. If it is, it returns the kernel symbol PAGE_SIZE, whose value depends on the architecture and machine model. Generally, one uses binaries that are dependent on the architecture but not on the machine model, in order to have a single binary distribution per architecture. This means that a user program should not find PAGE_SIZE at compile time from a header file, but use an actual system call, at least for those architectures (like sun4) where this dependency exists. Here glibc 2.0 fails because its getpagesize() returns a statically derived value, and does not use a system call. Things are OK in glibc 2.1.