opensem(2)     UNIX System V(Application Compatibility Package)      opensem(2)


NAME
      opensem - open a semaphore

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

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 (that is, 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)

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




























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