munmap(2)                                                            munmap(2)


NAME
     munmap - unmap pages of memory

SYNOPSIS
     #include <sys/types.h>
     #include <sys/mman.h>
     int munmap(void *addr, size_t len);

DESCRIPTION
     The function munmap removes the mappings for pages in the range [addr,
     addr + len).  Further references to these pages will result in the
     delivery of a SIGSEGV signal to the process.

     If the region being detached via munmap(2) belongs to a shared address
     space, and I/O is being done to this range by a process belonging to the
     same shared group, munmap(2) would fail returning EBUSY.  The specified
     virtual address range would not be unmapped from the shared address space
     unless it spans multiple contiguous regions in which case part of the
     address range (before the region causing the error) may be unmapped
     before EBUSY is returned.

     The function mmap often performs an implicit munmap.

     Note that when munmap is called by a process which is a member of a
     shared process group, the unmapping operation is relatively more
     expensive than it is for an independent process.  This is because the
     munmap system call must synchronize the removal of the address space with
     the other processes in the share group.  Refer to the sproc(2) manual
     entry for more information on shared process groups.

RETURN VALUE
     On success, munmap returns 0; on failure, munmap returns -1 and sets
     errno to indicate an error.

ERRORS
     Under the following conditions, the function munmap fails and sets errno
     to:

     EINVAL addr is not a multiple of the page size as returned by sysconf.

     EINVAL Addresses in the range [addr, addr + len) are outside the valid
            range for the address space of a process.

     EINVAL The argument len has a value less than or equal to 0.

     EBUSY  The address range specified has some active I/O initiated by some
            other process belonging to same share group.


SEE ALSO
     mmap(2), signal(2), sysconf(3C).


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