MUNMAP(3P) POSIX Programmer's Manual MUNMAP(3P)PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding
Linux manual page for details of Linux behavior), or the interface may
not be implemented on Linux.
munmap — unmap pages of memory
int munmap(void *addr, size_t len);
The munmap() function shall remove any mappings for those entire pages
containing any part of the address space of the process starting at
addr and continuing for len bytes. Further references to these pages
shall result in the generation of a SIGSEGV signal to the process. If
there are no mappings in the specified address range, then munmap() has
The implementation may require that addr be a multiple of the page size
as returned by sysconf().
If a mapping to be removed was private, any modifications made in this
address range shall be discarded.
Any memory locks (see mlock() and mlockall()) associated with this
address range shall be removed, as if by an appropriate call to
If a mapping removed from a typed memory object causes the correspond‐
ing address range of the memory pool to be inaccessible by any process
in the system except through allocatable mappings (that is, mappings of
typed memory objects opened with the POSIX_TYPED_MEM_MAP_ALLOCATABLE
flag), then that range of the memory pool shall become deallocated and
may become available to satisfy future typed memory allocation
A mapping removed from a typed memory object opened with the
POSIX_TYPED_MEM_MAP_ALLOCATABLE flag shall not affect in any way the
availability of that typed memory for allocation.
The behavior of this function is unspecified if the mapping was not
established by a call to mmap().
Upon successful completion, munmap() shall return 0; otherwise, it
shall return −1 and set errno to indicate the error.
The munmap() function shall fail if:
EINVAL Addresses in the range [addr,addr+len) are outside the valid
range for the address space of a process.
EINVAL The len argument is 0.
The munmap() function may fail if:
EINVAL The addr argument is not a multiple of the page size as returned
The following sections are informative.
The munmap() function corresponds to SVR4, just as the mmap() function
It is possible that an application has applied process memory locking
to a region that contains shared memory. If this has occurred, the mun‐
map() call ignores those locks and, if necessary, causes those locks to
Most implementations require that addr is a multiple of the page size
as returned by sysconf().
SEE ALSOmlock(), mlockall(), mmap(), posix_typed_mem_open(), sysconf()
The Base Definitions volume of POSIX.1‐2008, <sys_mman.h>
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.unix.org/online.html .
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IEEE/The Open Group 2013 MUNMAP(3P)