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Full Discussion: mmap
Homework and Emergencies Emergency UNIX and Linux Support mmap Post 302567484 by jim mcnamara on Monday 24th of October 2011 10:15:31 AM
Old 10-24-2011
Yes, you can allocate memory in one process and expose it to other processes. It is called shared memory. No, you cannot force another new process to use exclusively the memory you decide to give it.

All of this seems a little odd. You can cause yourself a lot of issues doing something like the above. What are you trying to accomplish, NOT what you think you should to do?
 

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MMAP2(2)						     Linux Programmer's Manual							  MMAP2(2)

NAME
mmap2 - map files or devices into memory SYNOPSIS
#include <sys/mman.h> void *mmap2(void *addr, size_t length, int prot, int flags, int fd, off_t pgoffset); DESCRIPTION
The mmap2() system call operates in exactly the same way as mmap(2), except that the final argument specifies the offset into the file in 4096-byte units (instead of bytes, as is done by mmap(2)). This enables applications that use a 32-bit off_t to map large files (up to 2^44 bytes). RETURN VALUE
On success, mmap2() returns a pointer to the mapped area. On error -1 is returned and errno is set appropriately. ERRORS
EFAULT Problem with getting the data from userspace. EINVAL (Various platforms where the page size is not 4096 bytes.) offset * 4096 is not a multiple of the system page size. mmap2() can return any of the same errors as mmap(2). VERSIONS
mmap2() is available since Linux 2.3.31. CONFORMING TO
This system call is Linux-specific. NOTES
Nowadays, the glibc mmap() wrapper function invokes this system call rather than the mmap(2) system call. On ia64, the unit for offset is actually the system page size, rather than 4096 bytes. SEE ALSO
getpagesize(2), mmap(2), mremap(2), msync(2), shm_open(3) COLOPHON
This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. Linux 2008-04-22 MMAP2(2)
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