mmap, munmap - map or unmap files or devices into memory

DESCRIPTION
WARNING: This is a BSD man page. Linux 0.99.11 can't map files, and can't do other things documented here. The function causes the pages starting at and continuing for at most bytes to be mapped from the object described by starting at byte offset If or is not a multiple of the pagesize, the mapped region may extend past the specified range. If is non-zero, it is used as a hint to the system. (As a convenience to the system, the actual address of the region may differ from the address supplied.) If is zero, an address will be selected by the system. The actual starting address of the region is returned. A successful deletes any previous mapping in the allocated address range. The protections (region accessibility) are specified in the argument by the following values: PROT_EXEC Pages may be executed. PROT_READ Pages may be read. PROT_WRITE Pages may be written. The parameter specifies the type of the mapped object, mapping options and whether modifications made to the mapped copy of the page are private to the process or are to be shared with other references. Sharing, mapping type and options are specified in the argument by the following values: MAP_ANON Map anonymous memory not associated with any specific file. The file descriptor used for creating MAP_ANON regions is used only for naming, and may be specified as -1 if no name is associated with the region. MAP_FILE Mapped from a regular file or character-special device memory. MAP_FIXED Do not permit the system to select a different address than the one specified. If the specified address cannot be used, will fail. If MAP_FIXED is specified, must be a multiple of the pagesize. Use of this option is discouraged. MAP_HASSEMAPHORE Notify the kernel that the region may contain semaphores and that special handling may be necessary. MAP_INHERIT Permit regions to be inherited across system calls. MAP_PRIVATE Modifications are private. MAP_SHARED Modifications are shared. The system call deletes the mappings for the specified address range, and causes further references to addresses within the range to generate invalid memory references. The current design does not allow a process to specify the location of swap space. In the future we may define an additional mapping type, in which the file descriptor argument specifies a file or device to which swapping should be done. Upon successful completion, returns a pointer to the mapped region. Otherwise, a value of -1 is returned and is set to indicate the error. For The flag PROT_READ was specified as part of the parameter and was not open for reading. The flags were specified as part of the and parameters and was not open for writing. is not a valid open file descriptor. One of or was not specified as part of the parameter. was specified and the parameter was not page aligned. Fd did not reference a regular or character special file. was specified and the parameter wasn't available. This is a BSD man page. Many of the details explained here are implemented under Linux. Please consult the Linux kernel source code for complete details on the current implementation of the function.