munmap(2) System Calls Manual munmap(2)NAME
munmap - Unmaps a mapped region
SYNOPSIS
#include <sys/mman.h>
int munmap ( void *addr, size_t len );
[Tru64 UNIX] The following definition of the munmap() function does not conform to current standards and is supported only for backward
compatibility (see standards(5)):
#include <sys/mman.h>
int munmap ( caddr_t addr, size_t len );
STANDARDS
Interfaces documented on this reference page conform to industry standards as follows:
munmap(): XSH5.0
Refer to the standards(5) reference page for more information about industry standards and associated tags.
PARAMETERS
Specifies the address of the region to be unmapped. Specifies the length in bytes of the region to be unmapped.
DESCRIPTION
The munmap() function unmaps a mapped file or shared memory region.
The addr and len parameters specify the address and length in bytes, respectively, of the region to be unmapped. The len parameter must be
a multiple of the page size as returned by sysconf(_SC_PAGE_SIZE). If len is not a multiple of the page size as returned by
sysconf(_SC_PAGE_SIZE), the length of the region will be rounded up to the next multiple of the page size.
The result of using an address which lies in an unmapped region and not in any subsequently mapped region is undefined.
RETURN VALUES
Upon successful completion, the munmap() function returns 0 (zero). Otherwise, munmap() returns -1 and sets errno to indicate the error.
ERRORS
If the munmap() function fails, errno may be set to one of the following values:
The range [addr, addr + len) includes an invalid address. The addr parameter is not a multiple of the page size as returned by
sysconf(_SC_PAGE_SIZE).
The len parameter is 0 (zero).
RELATED INFORMATION
Functions: mmap(2), sysconf(3)
Standards: standards(5) delim off
munmap(2)
Check Out this Related Man Page
MUNMAP(P) POSIX Programmer's Manual MUNMAP(P)
NAME
munmap - unmap pages of memory
SYNOPSIS
#include <sys/mman.h>
int munmap(void *addr, size_t len);
DESCRIPTION
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 no effect.
The implementation shall require that addr be a multiple of the page size {PAGESIZE}.
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
munlock().
If a mapping removed from a typed memory object causes the corresponding 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_ALLOCAT-
ABLE flag), then that range of the memory pool shall become deallocated and may become available to satisfy future typed memory allocation
requests.
A mapping removed from a typed memory object opened with the POSIX_TYPED_MEM_MAP_ALLOCATABLE flag shall not affect in any way the avail-
ability of that typed memory for allocation.
The behavior of this function is unspecified if the mapping was not established by a call to mmap().
RETURN VALUE
Upon successful completion, munmap() shall return 0; otherwise, it shall return -1 and set errno to indicate the error.
ERRORS
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.
EINVAL The addr argument is not a multiple of the page size as returned by sysconf().
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
The munmap() function is only supported if the Memory Mapped Files option or the Shared Memory Objects option is supported.
RATIONALE
The munmap() function corresponds to SVR4, just as the mmap() function does.
It is possible that an application has applied process memory locking to a region that contains shared memory. If this has occurred, the
munmap() call ignores those locks and, if necessary, causes those locks to be removed.
FUTURE DIRECTIONS
None.
SEE ALSO
mlock() , mlockall() , mmap() , posix_typed_mem_open() , sysconf() , the Base Definitions volume of IEEE Std 1003.1-2001, <signal.h>,
<sys/mman.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. 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.opengroup.org/unix/online.html .
IEEE /The Open Group 2003 MUNMAP(P)