SYS$CREMBX (OpenVMS) SYS$CREMBX (OpenVMS)
NAME
mkfifo, msgget, socket, wait - interprocess communications
SYS$CREMBX - Create a mailbox and assign a channel
DESCRIPTION
The mkfifo function creates a FIFO special file. The msgget function
creates a message queue or opens the message queue if the requested
queue already exists
EXPLAINATION
OpenVMS mailboxes and Digital UNIX message queues and FIFOs are similar
in that they all facilitate interprocess communication. FIFOs operate
on a sequental stream of bytes. The FIFO itself can be viewed in the
file system (by using the ls command). Access is controlled by the
file system protection. Any process with access to the FIFO special
file can open and read and write (depending upon the FIFO's protection)
to the file.
Message queues do not exist in the file system. Instead, they are
identified by a key. Messages in the message queue have distinct
boundries. Access to the message queue is defined at creation time but
can be changed by using the msgctl function. The unix domain socket
also exists in the file system. However, unix domain sockets must be
opened with the socket(2) function and thus can not be operated on with
the same ease as a FIFO. The unix domain socket allows either stream
or datagram comunication.
Digital UNIX also allows for network communication over internet TCP
and UDP sockets. Open VMS mailboxes can also be used to determine if
and how a process terminates, similar information is available from the
Digital UNIX wait, waitpid wait3, and wait4 system calls and by using
sigaction to request that the SIGCHLD signal be delivered to a process
when a child process terminates.
RELATED INFORMATION
Digital UNIX Functions:
open(2), mknod(2), msgctl(2), socket(2), tcp(7), udp(7), wait(2),
waitpid(2), wait3(2), wait4(2), sigaction(2), ls(1), intro(2) delim
off
SYS$CREMBX (OpenVMS)
