proctl(S)                      6 January 1993                      proctl(S)


 Name

    proctl - controls active processes or process groups

 Syntax


    cc  . . .  -lx


    #include <sys/proctl.h>

    int proctl(pid, command, arg)
    int pid, command;
    char *arg;


 Description

    proctl performs a variety of functions on active processes or process
    groups.  It has the same form as the ioctl(S) system call, except that a
    process ID (pid) is substituted for a file descriptor as the first param-
    eter.

    command is an integer mnemonic, specifying the action to be taken, and
    arg is a pointer to a data structure which defines the parameters associ-
    ated with the command if necessary.

    If pid is greater than zero (0), the command affects the process whose
    process ID is equal to pid.  pid may be 1.

    If pid is zero, the command is sent to all processes, except processes 0
    and 1 whose process group ID is equal to the process group ID of the
    sender.

    If pid is -1 and the effective user ID of the sender is not the super
    user, the command is sent to all processes, except processes 0 and 1
    whose real user ID is equal to the effective user ID of the sender.

    If pid is -1 and the effective user ID of the sender is super user, the
    command is sent to all processes except processes 0 and 1.

    If pid is negative but not -1, a signal is sent to all processes whose
    process group ID is equal to the absolute value of pid.

    proctl fails if one or more of the following are true:

    [EFAULT]       arg is not a valid address.

    [EINVAL]       command or arg is not valid.

    [ENOMEM]       The program has requested more memory than is available.

    [EPERM]        The user ID of the sending process is not super user, and
                   its real or effective user ID does not match the real or
                   effective user ID of the receiving process.

    [ESRCH]        No process can be found to match the specified pid.

 Memory restrictions

    exec(S) may fail when the required physical memory is larger than the
    available swap space. This restriction may be lifted using one of the
    following proctl commands:

    PRHUGEX

       Allows programs to be executed by this process even if they exceed the
       available swap space. Such programs must still fit in the available
       physical memory and the caller's effective user ID must be super user.
       Such HUGE processes are locked in memory to prevent them from being
       swapped.  Processes that are marked HUGE with this system call but are
       not greater than the size of the swapper behave normally but can
       expand into a HUGE, locked process.

    PRNORMEX

       Makes a process unable to exec(S) HUGE programs.  This call may be
       executed by any user. If an attempt is made to classify a process as
       normal using the PRNORMEX call when the process is already too big to
       swap, the proctl call fails, returning EINVAL.

    For example, you can use the following code to allow a process to be exe-
    cuted even if it exceeds the available memory swapping space:


       if (argc < 2) {

               fputs ("usage: runbig command arg ...\n", stderr);
               exit(2);

       }
       argv[argc] = 0;

       if (proctl(getpid(), PRHUGEX, (char *) 0) < 0) {

               perror ("runbig");
               exit(1);

       }


 Return value

    If an error has occurred, a value of -1 is returned and errno is set to
    indicate the error.

 See also

    exec(S), ioctl(S), kill(S)

 Standards conformance

    proctl is not part of any currently supported standard; it is an exten-
    sion of AT&T System V provided by the Santa Cruz Operation.