SEMOPEN(3) Linux Programmer's Manual SEMOPEN(3)

NAME
       semopen - initialize and open a named semaphore

SYNOPSIS
       #include            /* For O* constants */
       #include         /* For mode constants */
       #include 

       semt *semopen(const char *name, int oflag);
       semt *semopen(const char *name, int oflag,
                       modet mode, unsigned int value);

       Link with -pthread.

DESCRIPTION
       semopen()  creates  a  new  POSIX semaphore or opens an existing sema‐
       phore.  The semaphore is identified by name.  For details of  the  con‐
       struction of name, see semoverview(7).

       The  oflag  argument  specifies flags that control the operation of the
       call.  (Definitions of the flags values can be  obtained  by  including
       .)   If  OCREAT  is specified in oflag, then the semaphore is
       created if it does not already exist.  The owner (user ID) of the sema‐
       phore  is  set  to  the  effective user ID of the calling process.  The
       group ownership (group ID) is set to the  effective  group  ID  of  the
       calling  process.   If  both OCREAT and OEXCL are specified in oflag,
       then an error is returned if a semaphore with the  given  name  already
       exists.

       If OCREAT is specified in oflag, then two additional arguments must be
       supplied.  The mode argument specifies the permissions to be placed  on
       the  new semaphore, as for open(2).  (Symbolic definitions for the per‐
       missions bits can be obtained by including .)  The  permis‐
       sions  settings  are  masked  against the process umask.  Both read and
       write permission should be granted to each  class  of  user  that  will
       access  the  semaphore.  The value argument specifies the initial value
       for the new semaphore.  If OCREAT is specified, and a  semaphore  with
       the given name already exists, then mode and value are ignored.

RETURN VALUE
       On  success,  semopen() returns the address of the new semaphore; this
       address is used when calling  other  semaphore-related  functions.   On
       error,  semopen()  returns  SEMFAILED, with errno set to indicate the
       error.

ERRORS
       EACCES The semaphore exists, but the caller does not have permission to
              open it.

       EEXIST Both OCREAT and OEXCL were specified in oflag, but a semaphore
              with this name already exists.

       EINVAL value was greater than SEMVALUEMAX.

       EINVAL name consists of just "/", followed by no other characters.

       EMFILE The process already has the maximum number of files and open.

       ENAMETOOLONG
              name was too long.

       ENFILE The system limit on the total number  of  open  files  has  been
              reached.

       ENOENT The  OCREAT  flag  was  not specified in oflag and no semaphore
              with this name exists;  or,  OCREAT  was  specified,  but  name
              wasn't well formed.

       ENOMEM Insufficient memory.

CONFORMING TO
       POSIX.1-2001.

SEE ALSO
       semclose(3), semgetvalue(3), sempost(3), semunlink(3), semwait(3),
       semoverview(7)

COLOPHON
       This page is part of release 3.53 of the Linux  man-pages  project.   A
       description  of  the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.



Linux                             2012-05-13                       SEMOPEN(3)