---
name: "sys_mman.h"
section: "0p"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/sys_mman.h"
---

# sys\_mman.h(0p)

memory management declarations

## 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.

## NAME

sys/mman.h — memory management declarations

## SYNOPSIS

```
#include <sys/mman.h>
```

## DESCRIPTION

The *\<sys/mman.h\>* header shall define the following symbolic constants for use as protection options:

- PROT\_EXEC

  Page can be executed.

- PROT\_NONE

  Page cannot be accessed.

- PROT\_READ

  Page can be read.

- PROT\_WRITE

  Page can be written.

The *\<sys/mman.h\>* header shall define the following symbolic constants for use as flag options:

- MAP\_FIXED

  Interpret *addr* exactly.

- MAP\_PRIVATE

  Changes are private.

- MAP\_SHARED

  Share changes.

The *\<sys/mman.h\>* header shall define the following symbolic constants for the *msync*() function:

- MS\_ASYNC

  Perform asynchronous writes.

- MS\_INVALIDATE

  Invalidate mappings.

- MS\_SYNC

  Perform synchronous writes.

The *\<sys/mman.h\>* header shall define the following symbolic constants for the *mlockall*() function:

- MCL\_CURRENT

  Lock currently mapped pages.

- MCL\_FUTURE

  Lock pages that become mapped.

The *\<sys/mman.h\>* header shall define the symbolic constant MAP\_FAILED which shall have type **void \*** and shall be used to indicate a failure from the *mmap*() function .

If the Advisory Information option is supported, the *\<sys/mman.h\>* header shall define symbolic constants for the *advice* argument to the *posix\_madvise*() function as follows:

- POSIX\_MADV\_DONTNEED

  The application expects that it will not access the specified range in the near future.

- POSIX\_MADV\_NORMAL

  The application has no advice to give on its behavior with respect to the specified range. It is the default characteristic if no advice is given for a range of memory.

- POSIX\_MADV\_RANDOM

  The application expects to access the specified range in a random order.

- POSIX\_MADV\_SEQUENTIAL

  The application expects to access the specified range sequentially from lower addresses to higher addresses.

- POSIX\_MADV\_WILLNEED

  The application expects to access the specified range in the near future.

The *\<sys/mman.h\>* header shall define the following symbolic constants for use as flags for the *posix\_typed\_mem\_open*() function:

- POSIX\_TYPED\_MEM\_ALLOCATE

  Allocate on *mmap*().

- POSIX\_TYPED\_MEM\_ALLOCATE\_CONTIG

  Allocate contiguously on *mmap*().

- POSIX\_TYPED\_MEM\_MAP\_ALLOCATABLE

  Map on *mmap*(), without affecting allocatability.

The *\<sys/mman.h\>* header shall define the **mode\_t**, **off\_t**, and **size\_t** types as described in ***\<sys\_types.h\>***.

The *\<sys/mman.h\>* header shall define the **posix\_typed\_mem\_info** structure, which shall include at least the following member:

```
size_t  posix_tmi_length  Maximum length which may be allocated
                          from a typed memory object.
```

The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided.

```
int    mlock(const void *, size_t);
int    mlockall(int);
void  *mmap(void *, size_t, int, int, int, off_t);
int    mprotect(void *, size_t, int);
int    msync(void *, size_t, int);
int    munlock(const void *, size_t);
int    munlockall(void);
int    munmap(void *, size_t);
int    posix_madvise(void *, size_t, int);
int    posix_mem_offset(const void *restrict, size_t, off_t *restrict,
           size_t *restrict, int *restrict);
int    posix_typed_mem_get_info(int, struct posix_typed_mem_info *);
int    posix_typed_mem_open(const char *, int, int);
int    shm_open(const char *, int, mode_t);
int    shm_unlink(const char *);
```

*The following sections are informative.*

## APPLICATION USAGE

None.

## RATIONALE

None.

## FUTURE DIRECTIONS

None.

## SEE ALSO

***\<sys\_types.h\>***

The System Interfaces volume of POSIX.1‐2017, *mlock()*, *mlockall()*, *mmap()*, *mprotect()*, *msync()*, *munmap()*, *posix\_madvise()*, *posix\_mem\_offset()*, *posix\_typed\_mem\_get\_info()*, *posix\_typed\_mem\_open()*, *shm\_open()*, *shm\_unlink()*

## COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting\_bugs.html .