opensem(2)             (XENIX Compatibility Package)             opensem(2)


   NAME
         opensem - opens a semaphore

   SYNOPSIS
         cc [flag ...] file ... -lx
         int opensem(char *semname);

   DESCRIPTION
         opensem opens a semaphore named by sem_name and returns the unique
         semaphore identification number sem_num used by waitsem and sigsem.
         creatsem should always be called to initialize the semaphore before
         the first attempt to open it.

   DIAGNOSTICS
         opensem returns a value of -1 if an error occurs.  If the semaphore
         named does not exist, errno is set to ENOENT.  If the file specified
         is not a semaphore file (i.e., a file previously created by a process
         using a call to creatsem), errno is set to ENOTNAM.  If the semaphore
         has become invalid due to inappropriate use, errno is set to ENAVAIL.

   SEE ALSO
         creatsem(2), sigsem(2), waitsem(2).

   WARNING
         It is not advisable to open the same semaphore more than once.
         Although it is possible to do this, it may result in a serious
         deadlock.


























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