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  • Linux Man Page Viewer


    The following form allows you to view linux man pages.

    Command:

    shm_overview

    
    
    

    DESCRIPTION

           The POSIX shared memory API allows processes to communicate information
           by sharing a region of memory.
    
           The interfaces employed in the API are:
    
           shm_open(3)    Create and open  a  new  object,  or  open  an  existing
                          object.  This is analogous to open(2).  The call returns
                          a file descriptor for use by the other interfaces listed
                          below.
    
           ftruncate(2)   Set the size of the shared memory object.  (A newly cre-
                          ated shared memory object has a length of zero.)
    
           mmap(2)        Map the shared memory object into  the  virtual  address
                          space of the calling process.
    
           munmap(2)      Unmap  the shared memory object from the virtual address
                          space of the calling process.
    
           shm_unlink(3)  Remove a shared memory object name.
    
           close(2)       Close the file descriptor allocated by shm_open(3)  when
                          it is no longer needed.
    
           fstat(2)       Obtain a stat structure that describes the shared memory
                          object.  Among the information returned by this call are
                          the  object's  size  (st_size),  permissions  (st_mode),
                          owner (st_uid), and group (st_gid).
    
           fchown(2)      To change the ownership of a shared memory object.
    
           fchmod(2)      To change the permissions of a shared memory object.
    
       Versions
           POSIX shared memory is supported since Linux 2.4 and glibc 2.2.
    
       Persistence
           POSIX shared memory objects have kernel persistence:  a  shared  memory
           object will exist until the system is shut down, or until all processes
           have unmapped the object and it has been deleted with shm_unlink(3)
    
       Linking
           Programs using the POSIX shared memory API must  be  compiled  with  cc
           -lrt to link against the real-time library, librt.
    
       Accessing shared memory objects via the filesystem
           On  Linux,  shared  memory  objects  are  created  in a (tmpfs) virtual
           filesystem, normally mounted  under  /dev/shm.   Since  kernel  2.6.19,
           Linux  supports  the  use of access control lists (ACLs) to control the
           permissions of objects in the virtual filesystem.
    
           fchmod(2),  fchown(2),  fstat(2),  ftruncate(2),  mmap(2), mprotect(2),
           munmap(2),    shmget(2),    shmop(2),    shm_open(3),    shm_unlink(3),
           sem_overview(7)
    
    
    

    Linux 2010-09-10 SHM_OVERVIEW(7)

    
    
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