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sem_unlink (3)
  • sem_unlink (3) ( Solaris man: Библиотечные вызовы )
  • >> sem_unlink (3) ( FreeBSD man: Библиотечные вызовы )
  • sem_unlink (3) ( Linux man: Библиотечные вызовы )
  • sem_unlink (3) ( POSIX man: Библиотечные вызовы )

  • BSD mandoc
     

    NAME

    
    
    sem_open
    
     
    sem_close
    
     
    sem_unlink
    
     - named semaphore operations
    
     
    

    LIBRARY

    Lb libc
    
     
    

    SYNOPSIS

       #include <semaphore.h>
    sem_t * sem_open (const char *name int oflag ...);
    int sem_close (sem_t *sem);
    int sem_unlink (const char *name);
     

    DESCRIPTION

    The sem_open ();
    function creates or opens the named semaphore specified by Fa name . The returned semaphore may be used in subsequent calls to sem_getvalue3, sem_wait3, sem_trywait3, sem_post3, and sem_close (.);

    The following bits may be set in the Fa oflag argument:

    O_CREAT
    Create the semaphore if it does not already exist.

    The third argument to the call to sem_open ();
    must be of type Vt mode_t and specifies the mode for the semaphore. Only the S_IWUSR , S_IWGRP and S_IWOTH bits are examined; it is not possible to grant only ``read'' permission on a semaphore. The mode is modified according to the process's file creation mask; see umask(2).

    The fourth argument must be an Vt unsigned int and specifies the initial value for the semaphore, and must be no greater than SEM_VALUE_MAX

    O_EXCL
    Create the semaphore if it does not exist. If the semaphore already exists, sem_open ();
    will fail. This flag is ignored unless O_CREAT is also specified.

    The sem_close ();
    function closes a named semaphore that was opened by a call to sem_open (.);

    The sem_unlink ();
    function removes the semaphore named Fa name . Resources allocated to the semaphore are only deallocated when all processes that have the semaphore open close it.  

    RETURN VALUES

    If successful, the sem_open ();
    function returns the address of the opened semaphore. If the same Fa name argument is given to multiple calls to sem_open ();
    by the same process without an intervening call to sem_close (,);
    the same address is returned each time. If the semaphore cannot be opened, sem_open ();
    returns SEM_FAILED and the global variable errno is set to indicate the error.

    Rv -std sem_close sem_unlink  

    ERRORS

    The sem_open ();
    function will fail if:

    Bq Er EACCES
    The semaphore exists and the permissions specified by Fa oflag at the time it was created deny access to this process.
    Bq Er EACCES
    The semaphore does not exist, but permission to create it is denied.
    Bq Er EEXIST
    O_CREAT and O_EXCL are set but the semaphore already exists.
    Bq Er EINTR
    The call was interrupted by a signal.
    Bq Er EINVAL
    The sem_open ();
    operation is not supported for the given Fa name .
    Bq Er EINVAL
    The Fa value argument is greater than SEM_VALUE_MAX
    Bq Er ENAMETOOLONG
    The Fa name argument is too long.
    Bq Er ENFILE
    The system limit on semaphores has been reached.
    Bq Er ENOENT
    O_CREAT is not set but the named semaphore does not exist.
    Bq Er ENOSPC
    There is not enough space to create the semaphore.

    The sem_close ();
    function will fail if:

    Bq Er EINVAL
    The Fa sem argument is not a valid semaphore.

    The sem_unlink ();
    function will fail if:

    Bq Er EACCES
    Permission is denied to unlink the semaphore.
    Bq Er ENAMETOOLONG
    The specified Fa name is too long.
    Bq Er ENOENT
    The named semaphore does not exist.

     

    SEE ALSO

    close(2), open(2), umask(2), unlink(2), sem_getvalue3, sem_post3, sem_trywait3, sem_wait3, sem(4)  

    STANDARDS

    The sem_open (,);
    sem_close (,);
    and sem_unlink ();
    functions conform to St -p1003.1-96 .  

    HISTORY

    Support for named semaphores first appeared in Fx 5.0 .  

    BUGS

    This implementation places strict requirements on the value of Fa name : it must begin with a slash (`/' ) contain no other slash characters, and be less than 14 characters in length not including the terminating null character.


     

    Index

    NAME
    LIBRARY
    SYNOPSIS
    DESCRIPTION
    RETURN VALUES
    ERRORS
    SEE ALSO
    STANDARDS
    HISTORY
    BUGS


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