Creates a session and sets the process group ID.

    This function is supported on OpenVMS Integrity servers and
    Alpha only.

    Format

      #include  <unistd.h>

      pid_t setsid  (void);

1  –  Description

    The setsid function creates a new session if the calling process
    is not a process group leader. Upon return, the calling process
    is the session leader of this new session and the process
    group leader of a new process group, and it has no controlling
    terminal. The process group ID of the calling process is set
    equal to the process ID of the calling process. The calling
    process is the only process in the new process group and the
    only process in the new session.

    This function requires that long (32-bit) UID/GID support be
    enabled. See 32-Bit UID and GID Macro (Integrity servers, Alpha)
    for more information.

2  –  Return Values

    x                  The process group ID of the calling process.
    (pid_t)-1          Indicates an error. The function sets errno to
                       the following value:

                       o  EPERM - The calling process is already a
                          process group leader, or the process group
                          ID of a process other than the calling
                          process matches the process ID of the
                          calling process.