Sets the process group ID for job control.

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

    Format

      #include  <unistd.h>

      int setpgid  (pid_t pid, pid_t pgid);

1  –  Arguments

 pid

    The process ID for which the process group ID is to be set.

 pgid

    The value to which the process group ID is set.

2  –  Description

    The setpgid function is used either to join an existing process
    group or create a new process group within the session of the
    calling process. The process group ID of a session leader will
    not change.

    Upon successful completion, the process group ID of the process
    with a process ID of pid is set to pgid. As a special case, if
    pid is 0, the process ID of the calling process is used. Also, if
    pgid is 0, the process group ID of the indicated process is used.

    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.

3  –  Return Values

    0                  Successful completion.
    -1                 Indicates an error. The function sets errno to
                       one of the following values:

                       o  EACCES - The value of the pid argument
                          matches the process ID of a child process
                          of the calling process and the child
                          process has successfully executed one of
                          the exec functions.

                       o  EINVAL - The value of the pgid argument is
                          less than 0, or is not a value supported by
                          the implementation.

                       o  EPERM - The process indicated by the pid
                          argument is a session leader. The value
                          of the pid argument matches the process ID
                          of a child process of the calling process,
                          and the child process is not in the same
                          session as the calling process. The value
                          of the pgid argument is valid but does
                          not match the process ID of the process
                          indicated by the pid argument, and there
                          is no process with a process group ID that
                          matches the value of the pgid argument in
                          the same session as the calling process.

                       o  ESRCH - The value of the pid argument does
                          not match the process ID of the calling
                          process or of a child process of the
                          calling process.