process.c

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/**********************************************************************

  process.c -

  $Author: akr $
  $Date: 2005/11/20 03:30:47 $
  created at: Tue Aug 10 14:30:50 JST 1993

  Copyright (C) 1993-2003 Yukihiro Matsumoto
  Copyright (C) 2000  Network Applied Communication Laboratory, Inc.
  Copyright (C) 2000  Information-technology Promotion Agency, Japan

**********************************************************************/

#include "ruby.h"
#include "rubysig.h"
#include <stdio.h>
#include <errno.h>
#include <signal.h>
#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef __DJGPP__
#include <process.h>
#endif

#include <time.h>
#include <ctype.h>

#ifndef EXIT_SUCCESS
#define EXIT_SUCCESS 0
#endif
#ifndef EXIT_FAILURE
#define EXIT_FAILURE 1
#endif

struct timeval rb_time_interval (VALUE);

#ifdef HAVE_SYS_WAIT_H
# include <sys/wait.h>
#endif
#ifdef HAVE_GETPRIORITY
# include <sys/resource.h>
#endif
#include "st.h"

#ifdef __EMX__
#undef HAVE_GETPGRP
#endif

#ifdef HAVE_SYS_TIMES_H
#include <sys/times.h>
#endif

#ifdef HAVE_GRP_H
#include <grp.h>
#endif

#if defined(HAVE_TIMES) || defined(_WIN32)
static VALUE S_Tms;
#endif

#ifndef WIFEXITED
#define WIFEXITED(w)    (((w) & 0xff) == 0)
#endif
#ifndef WIFSIGNALED
#define WIFSIGNALED(w)  (((w) & 0x7f) > 0 && (((w) & 0x7f) < 0x7f))
#endif
#ifndef WIFSTOPPED
#define WIFSTOPPED(w)   (((w) & 0xff) == 0x7f)
#endif
#ifndef WEXITSTATUS
#define WEXITSTATUS(w)  (((w) >> 8) & 0xff)
#endif
#ifndef WTERMSIG
#define WTERMSIG(w)     ((w) & 0x7f)
#endif
#ifndef WSTOPSIG
#define WSTOPSIG        WEXITSTATUS
#endif

#if defined(__APPLE__) && ( defined(__MACH__) || defined(__DARWIN__) ) && !defined(__MacOS_X__)
#define __MacOS_X__ 1
#endif

#if defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) || defined(__bsdi__)
#define HAVE_44BSD_SETUID 1
#define HAVE_44BSD_SETGID 1
#endif

#ifdef __NetBSD__
#undef HAVE_SETRUID
#undef HAVE_SETRGID
#endif

#if defined(__MacOS_X__) || defined(__bsdi__)
#define BROKEN_SETREUID 1
#define BROKEN_SETREGID 1
#endif

#if defined(HAVE_44BSD_SETUID) || defined(__MacOS_X__)
#if !defined(USE_SETREUID) && !defined(BROKEN_SETREUID)
#define OBSOLETE_SETREUID 1
#endif
#if !defined(USE_SETREGID) && !defined(BROKEN_SETREGID)
#define OBSOLETE_SETREGID 1
#endif
#endif


/*
 *  call-seq:
 *     Process.pid   => fixnum
 *
 *  Returns the process id of this process. Not available on all
 *  platforms.
 *
 *     Process.pid   #=> 27415
 */

static VALUE
get_pid()
{
    rb_secure(2);
    return INT2FIX(getpid());
}


/*
 *  call-seq:
 *     Process.ppid   => fixnum
 *
 *  Returns the process id of the parent of this process. Always
 *  returns 0 on NT. Not available on all platforms.
 *
 *     puts "I am #{Process.pid}"
 *     Process.fork { puts "Dad is #{Process.ppid}" }
 *
 *  <em>produces:</em>
 *
 *     I am 27417
 *     Dad is 27417
 */

static VALUE
get_ppid()
{
    rb_secure(2);
#ifdef _WIN32
    return INT2FIX(0);
#else
    return INT2FIX(getppid());
#endif
}


/*********************************************************************
 *
 * Document-class: Process::Status
 *
 *  <code>Process::Status</code> encapsulates the information on the
 *  status of a running or terminated system process. The built-in
 *  variable <code>$?</code> is either +nil+ or a
 *  <code>Process::Status</code> object.
 *
 *     fork { exit 99 }   #=> 26557
 *     Process.wait       #=> 26557
 *     $?.class           #=> Process::Status
 *     $?.to_i            #=> 25344
 *     $? >> 8            #=> 99
 *     $?.stopped?        #=> false
 *     $?.exited?         #=> true
 *     $?.exitstatus      #=> 99
 *
 *  Posix systems record information on processes using a 16-bit
 *  integer.  The lower bits record the process status (stopped,
 *  exited, signaled) and the upper bits possibly contain additional
 *  information (for example the program's return code in the case of
 *  exited processes). Pre Ruby 1.8, these bits were exposed directly
 *  to the Ruby program. Ruby now encapsulates these in a
 *  <code>Process::Status</code> object. To maximize compatibility,
 *  however, these objects retain a bit-oriented interface. In the
 *  descriptions that follow, when we talk about the integer value of
 *  _stat_, we're referring to this 16 bit value.
 */

static VALUE rb_cProcStatus;
VALUE rb_last_status = Qnil;

static void
last_status_set(status, pid)
    int status, pid;
{
    rb_last_status = rb_obj_alloc(rb_cProcStatus);
    rb_iv_set(rb_last_status, "status", INT2FIX(status));
    rb_iv_set(rb_last_status, "pid", INT2FIX(pid));
}


/*
 *  call-seq:
 *     stat.to_i     => fixnum
 *     stat.to_int   => fixnum
 *
 *  Returns the bits in _stat_ as a <code>Fixnum</code>. Poking
 *  around in these bits is platform dependent.
 *
 *     fork { exit 0xab }         #=> 26566
 *     Process.wait               #=> 26566
 *     sprintf('%04x', $?.to_i)   #=> "ab00"
 */

static VALUE
pst_to_i(st)
    VALUE st;
{
    return rb_iv_get(st, "status");
}


/*
 *  call-seq:
 *     stat.to_s   => string
 *
 *  Equivalent to _stat_<code>.to_i.to_s</code>.
 */

static VALUE
pst_to_s(st)
    VALUE st;
{
    return rb_fix2str(pst_to_i(st), 10);
}


/*
 *  call-seq:
 *     stat.pid   => fixnum
 *
 *  Returns the process ID that this status object represents.
 *
 *     fork { exit }   #=> 26569
 *     Process.wait    #=> 26569
 *     $?.pid          #=> 26569
 */

static VALUE
pst_pid(st)
    VALUE st;
{
    return rb_iv_get(st, "pid");
}


/*
 *  call-seq:
 *     stat.inspect   => string
 *
 *  Override the inspection method.
 */

static VALUE
pst_inspect(st)
    VALUE st;
{
    VALUE pid;
    int status;
    VALUE str;
    char buf[256];

    pid = pst_pid(st);
    status = NUM2INT(st);

    snprintf(buf, sizeof(buf), "#<%s: pid=%ld", rb_class2name(CLASS_OF(st)), NUM2LONG(pid));
    str = rb_str_new2(buf);
    if (WIFSTOPPED(status)) {
        int stopsig = WSTOPSIG(status);
        const char *signame = ruby_signal_name(stopsig);
        if (signame) {
            snprintf(buf, sizeof(buf), ",stopped(SIG%s=%d)", signame, stopsig);
        }
        else {
            snprintf(buf, sizeof(buf), ",stopped(%d)", stopsig);
        }
        rb_str_cat2(str, buf);
    }
    if (WIFSIGNALED(status)) {
        int termsig = WTERMSIG(status);
        const char *signame = ruby_signal_name(termsig);
        if (signame) {
            snprintf(buf, sizeof(buf), ",signaled(SIG%s=%d)", signame, termsig);
        }
        else {
            snprintf(buf, sizeof(buf), ",signaled(%d)", termsig);
        }
        rb_str_cat2(str, buf);
    }
    if (WIFEXITED(status)) {
        snprintf(buf, sizeof(buf), ",exited(%d)", WEXITSTATUS(status));
        rb_str_cat2(str, buf);
    }
#ifdef WCOREDUMP
    if (WCOREDUMP(status)) {
        rb_str_cat2(str, ",coredumped");
    }
#endif
    rb_str_cat2(str, ">");
    return str;
}


/*
 *  call-seq:
 *     stat == other   => true or false
 *
 *  Returns +true+ if the integer value of _stat_
 *  equals <em>other</em>.
 */

static VALUE
pst_equal(st1, st2)
    VALUE st1, st2;
{
    if (st1 == st2) return Qtrue;
    return rb_equal(pst_to_i(st1), st2);
}


/*
 *  call-seq:
 *     stat & num   => fixnum
 *
 *  Logical AND of the bits in _stat_ with <em>num</em>.
 *
 *     fork { exit 0x37 }
 *     Process.wait
 *     sprintf('%04x', $?.to_i)       #=> "3700"
 *     sprintf('%04x', $? & 0x1e00)   #=> "1600"
 */

static VALUE
pst_bitand(st1, st2)
    VALUE st1, st2;
{
    int status = NUM2INT(st1) & NUM2INT(st2);

    return INT2NUM(status);
}


/*
 *  call-seq:
 *     stat >> num   => fixnum
 *
 *  Shift the bits in _stat_ right <em>num</em> places.
 *
 *     fork { exit 99 }   #=> 26563
 *     Process.wait       #=> 26563
 *     $?.to_i            #=> 25344
 *     $? >> 8            #=> 99
 */

static VALUE
pst_rshift(st1, st2)
    VALUE st1, st2;
{
    int status = NUM2INT(st1) >> NUM2INT(st2);

    return INT2NUM(status);
}


/*
 *  call-seq:
 *     stat.stopped?   => true or false
 *
 *  Returns +true+ if this process is stopped. This is only
 *  returned if the corresponding <code>wait</code> call had the
 *  <code>WUNTRACED</code> flag set.
 */

static VALUE
pst_wifstopped(st)
    VALUE st;
{
    int status = NUM2INT(st);

    if (WIFSTOPPED(status))
        return Qtrue;
    else
        return Qfalse;
}


/*
 *  call-seq:
 *     stat.stopsig   => fixnum or nil
 *
 *  Returns the number of the signal that caused _stat_ to stop
 *  (or +nil+ if self is not stopped).
 */

static VALUE
pst_wstopsig(st)
    VALUE st;
{
    int status = NUM2INT(st);

    if (WIFSTOPPED(status))
        return INT2NUM(WSTOPSIG(status));
    return Qnil;
}


/*
 *  call-seq:
 *     stat.signaled?   => true or false
 *
 *  Returns +true+ if _stat_ terminated because of
 *  an uncaught signal.
 */

static VALUE
pst_wifsignaled(st)
    VALUE st;
{
    int status = NUM2INT(st);

    if (WIFSIGNALED(status))
        return Qtrue;
    else
        return Qfalse;
}


/*
 *  call-seq:
 *     stat.termsig   => fixnum or nil
 *
 *  Returns the number of the signal that caused _stat_ to
 *  terminate (or +nil+ if self was not terminated by an
 *  uncaught signal).
 */

static VALUE
pst_wtermsig(st)
    VALUE st;
{
    int status = NUM2INT(st);

    if (WIFSIGNALED(status))
        return INT2NUM(WTERMSIG(status));
    return Qnil;
}


/*
 *  call-seq:
 *     stat.exited?   => true or false
 *
 *  Returns +true+ if _stat_ exited normally (for
 *  example using an <code>exit()</code> call or finishing the
 *  program).
 */

static VALUE
pst_wifexited(st)
    VALUE st;
{
    int status = NUM2INT(st);

    if (WIFEXITED(status))
        return Qtrue;
    else
        return Qfalse;
}


/*
 *  call-seq:
 *     stat.exitstatus   => fixnum or nil
 *
 *  Returns the least significant eight bits of the return code of
 *  _stat_. Only available if <code>exited?</code> is
 *  +true+.
 *
 *     fork { }           #=> 26572
 *     Process.wait       #=> 26572
 *     $?.exited?         #=> true
 *     $?.exitstatus      #=> 0
 *
 *     fork { exit 99 }   #=> 26573
 *     Process.wait       #=> 26573
 *     $?.exited?         #=> true
 *     $?.exitstatus      #=> 99
 */

static VALUE
pst_wexitstatus(st)
    VALUE st;
{
    int status = NUM2INT(st);

    if (WIFEXITED(status))
        return INT2NUM(WEXITSTATUS(status));
    return Qnil;
}


/*
 *  call-seq:
 *     stat.success?   => true, false or nil
 *
 *  Returns +true+ if _stat_ is successful, +false+ if not.
 *  Returns +nil+ if <code>exited?</code> is not +true+.
 */

static VALUE
pst_success_p(st)
    VALUE st;
{
    int status = NUM2INT(st);

    if (!WIFEXITED(status))
        return Qnil;
    return WEXITSTATUS(status) == EXIT_SUCCESS ? Qtrue : Qfalse;
}


/*
 *  call-seq:
 *     stat.coredump?   => true or false
 *
 *  Returns +true+ if _stat_ generated a coredump
 *  when it terminated. Not available on all platforms.
 */

static VALUE
pst_wcoredump(st)
    VALUE st;
{
#ifdef WCOREDUMP
    int status = NUM2INT(st);

    if (WCOREDUMP(status))
        return Qtrue;
    else
        return Qfalse;
#else
    return Qfalse;
#endif
}

#if !defined(HAVE_WAITPID) && !defined(HAVE_WAIT4)
#define NO_WAITPID
static st_table *pid_tbl;
#endif

int
rb_waitpid(pid, st, flags)
    int pid;
    int *st;
    int flags;
{
    int result;
#ifndef NO_WAITPID
    int oflags = flags;
    if (!rb_thread_alone()) {   /* there're other threads to run */
        flags |= WNOHANG;
    }

  retry:
    TRAP_BEG;
#ifdef HAVE_WAITPID
    result = waitpid(pid, st, flags);
#else  /* HAVE_WAIT4 */
    result = wait4(pid, st, flags, NULL);
#endif
    TRAP_END;
    if (result < 0) {
        if (errno == EINTR) {
            rb_thread_polling();
            goto retry;
        }
        return -1;
    }
    if (result == 0) {
        if (oflags & WNOHANG) return 0;
        rb_thread_polling();
        if (rb_thread_alone()) flags = oflags;
        goto retry;
    }
#else  /* NO_WAITPID */
    if (pid_tbl && st_lookup(pid_tbl, pid, st)) {
        last_status_set(*st, pid);
        st_delete(pid_tbl, (st_data_t*)&pid, NULL);
        return pid;
    }

    if (flags) {
        rb_raise(rb_eArgError, "can't do waitpid with flags");
    }

    for (;;) {
        TRAP_BEG;
        result = wait(st);
        TRAP_END;
        if (result < 0) {
            if (errno == EINTR) {
                rb_thread_schedule();
                continue;
            }
            return -1;
        }
        if (result == pid) {
            break;
        }
        if (!pid_tbl)
            pid_tbl = st_init_numtable();
        st_insert(pid_tbl, pid, st);
        if (!rb_thread_alone()) rb_thread_schedule();
    }
#endif
    if (result > 0) {
        last_status_set(*st, result);
    }
    return result;
}

#ifdef NO_WAITPID
struct wait_data {
    int pid;
    int status;
};

static int
wait_each(pid, status, data)
    int pid, status;
    struct wait_data *data;
{
    if (data->status != -1) return ST_STOP;

    data->pid = pid;
    data->status = status;
    return ST_DELETE;
}

static int
waitall_each(pid, status, ary)
    int pid, status;
    VALUE ary;
{
    last_status_set(status, pid);
    rb_ary_push(ary, rb_assoc_new(INT2NUM(pid), rb_last_status));
    return ST_DELETE;
}
#endif


/* [MG]:FIXME: I wasn't sure how this should be done, since ::wait()
   has historically been documented as if it didn't take any arguments
   despite the fact that it's just an alias for ::waitpid(). The way I
   have it below is more truthful, but a little confusing.

   I also took the liberty of putting in the pid values, as they're
   pretty useful, and it looked as if the original 'ri' output was
   supposed to contain them after "[...]depending on the value of
   aPid:".

   The 'ansi' and 'bs' formats of the ri output don't display the
   definition list for some reason, but the plain text one does.
 */

/*
 *  call-seq:
 *     Process.wait()                     => fixnum
 *     Process.wait(pid=-1, flags=0)      => fixnum
 *     Process.waitpid(pid=-1, flags=0)   => fixnum
 *
 *  Waits for a child process to exit, returns its process id, and
 *  sets <code>$?</code> to a <code>Process::Status</code> object
 *  containing information on that process. Which child it waits on
 *  depends on the value of _pid_:
 *
 *  > 0::   Waits for the child whose process ID equals _pid_.
 *
 *  0::     Waits for any child whose process group ID equals that of the
 *          calling process.
 *
 *  -1::    Waits for any child process (the default if no _pid_ is
 *          given).
 *
 *  < -1::  Waits for any child whose process group ID equals the absolute
 *          value of _pid_.
 *
 *  The _flags_ argument may be a logical or of the flag values
 *  <code>Process::WNOHANG</code> (do not block if no child available)
 *  or <code>Process::WUNTRACED</code> (return stopped children that
 *  haven't been reported). Not all flags are available on all
 *  platforms, but a flag value of zero will work on all platforms.
 *
 *  Calling this method raises a <code>SystemError</code> if there are
 *  no child processes. Not available on all platforms.
 *
 *     include Process
 *     fork { exit 99 }                 #=> 27429
 *     wait                             #=> 27429
 *     $?.exitstatus                    #=> 99
 *
 *     pid = fork { sleep 3 }           #=> 27440
 *     Time.now                         #=> Wed Apr 09 08:57:09 CDT 2003
 *     waitpid(pid, Process::WNOHANG)   #=> nil
 *     Time.now                         #=> Wed Apr 09 08:57:09 CDT 2003
 *     waitpid(pid, 0)                  #=> 27440
 *     Time.now                         #=> Wed Apr 09 08:57:12 CDT 2003
 */

static VALUE
proc_wait(argc, argv)
    int argc;
    VALUE *argv;
{
    VALUE vpid, vflags;
    int pid, flags, status;

    rb_secure(2);
    flags = 0;
    rb_scan_args(argc, argv, "02", &vpid, &vflags);
    if (argc == 0) {
        pid = -1;
    }
    else {
        pid = NUM2INT(vpid);
        if (argc == 2 && !NIL_P(vflags)) {
            flags = NUM2UINT(vflags);
        }
    }
    if ((pid = rb_waitpid(pid, &status, flags)) < 0)
        rb_sys_fail(0);
    if (pid == 0) {
        return rb_last_status = Qnil;
    }
    return INT2FIX(pid);
}


/*
 *  call-seq:
 *     Process.wait2(pid=-1, flags=0)      => [pid, status]
 *     Process.waitpid2(pid=-1, flags=0)   => [pid, status]
 *
 *  Waits for a child process to exit (see Process::waitpid for exact
 *  semantics) and returns an array containing the process id and the
 *  exit status (a <code>Process::Status</code> object) of that
 *  child. Raises a <code>SystemError</code> if there are no child
 *  processes.
 *
 *     Process.fork { exit 99 }   #=> 27437
 *     pid, status = Process.wait2
 *     pid                        #=> 27437
 *     status.exitstatus          #=> 99
 */

static VALUE
proc_wait2(argc, argv)
    int argc;
    VALUE *argv;
{
    VALUE pid = proc_wait(argc, argv);
    if (NIL_P(pid)) return Qnil;
    return rb_assoc_new(pid, rb_last_status);
}


/*
 *  call-seq:
 *     Process.waitall   => [ [pid1,status1], ...]
 *
 *  Waits for all children, returning an array of
 *  _pid_/_status_ pairs (where _status_ is a
 *  <code>Process::Status</code> object).
 *
 *     fork { sleep 0.2; exit 2 }   #=> 27432
 *     fork { sleep 0.1; exit 1 }   #=> 27433
 *     fork {            exit 0 }   #=> 27434
 *     p Process.waitall
 *
 *  <em>produces</em>:
 *
 *     [[27434, #<Process::Status: pid=27434,exited(0)>],
 *      [27433, #<Process::Status: pid=27433,exited(1)>],
 *      [27432, #<Process::Status: pid=27432,exited(2)>]]
 */

static VALUE
proc_waitall()
{
    VALUE result;
    int pid, status;

    rb_secure(2);
    result = rb_ary_new();
#ifdef NO_WAITPID
    if (pid_tbl) {
        st_foreach(pid_tbl, waitall_each, result);
    }

    for (pid = -1;;) {
        pid = wait(&status);
        if (pid == -1) {
            if (errno == ECHILD)
                break;
            if (errno == EINTR) {
                rb_thread_schedule();
                continue;
            }
            rb_sys_fail(0);
        }
        last_status_set(status, pid);
        rb_ary_push(result, rb_assoc_new(INT2NUM(pid), rb_last_status));
    }
#else
    rb_last_status = Qnil;
    for (pid = -1;;) {
        pid = rb_waitpid(-1, &status, 0);
        if (pid == -1) {
            if (errno == ECHILD)
                break;
            rb_sys_fail(0);
        }
        rb_ary_push(result, rb_assoc_new(INT2NUM(pid), rb_last_status));
    }
#endif
    return result;
}

static VALUE
detach_process_watcher(pid_p)
    int *pid_p;
{
    int cpid, status;

    for (;;) {
        cpid = rb_waitpid(*pid_p, &status, WNOHANG);
        if (cpid != 0) return Qnil;
        rb_thread_sleep(1);
    }
}

VALUE
rb_detach_process(pid)
    int pid;
{
    return rb_thread_create(detach_process_watcher, (void*)&pid);
}


/*
 *  call-seq:
 *     Process.detach(pid)   => thread
 *
 *  Some operating systems retain the status of terminated child
 *  processes until the parent collects that status (normally using
 *  some variant of <code>wait()</code>. If the parent never collects
 *  this status, the child stays around as a <em>zombie</em> process.
 *  <code>Process::detach</code> prevents this by setting up a
 *  separate Ruby thread whose sole job is to reap the status of the
 *  process _pid_ when it terminates. Use <code>detach</code>
 *  only when you do not intent to explicitly wait for the child to
 *  terminate.  <code>detach</code> only checks the status
 *  periodically (currently once each second).
 *
 *  In this first example, we don't reap the first child process, so
 *  it appears as a zombie in the process status display.
 *
 *     p1 = fork { sleep 0.1 }
 *     p2 = fork { sleep 0.2 }
 *     Process.waitpid(p2)
 *     sleep 2
 *     system("ps -ho pid,state -p #{p1}")
 *
 *  <em>produces:</em>
 *
 *     27389 Z
 *
 *  In the next example, <code>Process::detach</code> is used to reap
 *  the child automatically.
 *
 *     p1 = fork { sleep 0.1 }
 *     p2 = fork { sleep 0.2 }
 *     Process.detach(p1)
 *     Process.waitpid(p2)
 *     sleep 2
 *     system("ps -ho pid,state -p #{p1}")
 *
 *  <em>(produces no output)</em>
 */

static VALUE
proc_detach(VALUE obj, VALUE pid)
{
    rb_secure(2);
    return rb_detach_process(NUM2INT(pid));
}

#ifndef HAVE_STRING_H
char *strtok();
#endif

#ifdef HAVE_SETITIMER
#define before_exec() rb_thread_stop_timer()
#define after_exec() rb_thread_start_timer()
#else
#define before_exec()
#define after_exec()
#endif

extern char *dln_find_exe();

static void
security(str)
    char *str;
{
    if (rb_env_path_tainted()) {
        if (rb_safe_level() > 0) {
            rb_raise(rb_eSecurityError, "Insecure PATH - %s", str);
        }
    }
}

static int
proc_exec_v(argv, prog)
    char **argv;
    char *prog;
{
    if (!prog)
        prog = argv[0];
    security(prog);
    prog = dln_find_exe(prog, 0);
    if (!prog)
        return -1;

#if (defined(MSDOS) && !defined(DJGPP)) || defined(__human68k__) || defined(__EMX__) || defined(OS2)
    {
#if defined(__human68k__)
#define COMMAND "command.x"
#endif
#if defined(__EMX__) || defined(OS2) /* OS/2 emx */
#define COMMAND "cmd.exe"
#endif
#if (defined(MSDOS) && !defined(DJGPP))
#define COMMAND "command.com"
#endif
        char *extension;

        if ((extension = strrchr(prog, '.')) != NULL && strcasecmp(extension, ".bat") == 0) {
            char **new_argv;
            char *p;
            int n;

            for (n = 0; argv[n]; n++)
                /* no-op */;
            new_argv = ALLOCA_N(char*, n + 2);
            for (; n > 0; n--)
                new_argv[n + 1] = argv[n];
            new_argv[1] = strcpy(ALLOCA_N(char, strlen(argv[0]) + 1), argv[0]);
            for (p = new_argv[1]; *p != '\0'; p++)
                if (*p == '/')
                    *p = '\\';
            new_argv[0] = COMMAND;
            argv = new_argv;
            prog = dln_find_exe(argv[0], 0);
            if (!prog) {
                errno = ENOENT;
                return -1;
            }
        }
    }
#endif /* MSDOS or __human68k__ or __EMX__ */
    before_exec();
    execv(prog, argv);
    after_exec();
    return -1;
}

static int
proc_exec_n(argc, argv, progv)
    int argc;
    VALUE *argv;
    VALUE progv;
{
    char *prog = 0;
    char **args;
    int i;

    if (progv) {
        prog = RSTRING(progv)->ptr;
    }
    args = ALLOCA_N(char*, argc+1);
    for (i=0; i<argc; i++) {
        SafeStringValue(argv[i]);
        args[i] = RSTRING(argv[i])->ptr;
    }
    args[i] = 0;
    if (args[0]) {
        return proc_exec_v(args, prog);
    }
    return -1;
}

int
rb_proc_exec(str)
    const char *str;
{
    const char *s = str;
    char *ss, *t;
    char **argv, **a;

    while (*str && ISSPACE(*str))
        str++;

#ifdef _WIN32
    before_exec();
    do_spawn(P_OVERLAY, (char *)str);
    after_exec();
#else
    for (s=str; *s; s++) {
        if (*s != ' ' && !ISALPHA(*s) && strchr("*?{}[]<>()~&|\\$;'`\"\n",*s)) {
#if defined(MSDOS)
            int status;
            before_exec();
            status = system(str);
            after_exec();
            if (status != -1)
                exit(status);
#else
#if defined(__human68k__) || defined(__CYGWIN32__) || defined(__EMX__)
            char *shell = dln_find_exe("sh", 0);
            int status = -1;
            before_exec();
            if (shell)
                execl(shell, "sh", "-c", str, (char *) NULL);
            else
                status = system(str);
            after_exec();
            if (status != -1)
                exit(status);
#else
            before_exec();
            execl("/bin/sh", "sh", "-c", str, (char *)NULL);
            after_exec();
#endif
#endif
            return -1;
        }
    }
    a = argv = ALLOCA_N(char*, (s-str)/2+2);
    ss = ALLOCA_N(char, s-str+1);
    strcpy(ss, str);
    if (*a++ = strtok(ss, " \t")) {
        while (t = strtok(NULL, " \t")) {
            *a++ = t;
        }
        *a = NULL;
    }
    if (argv[0]) {
        return proc_exec_v(argv, 0);
    }
    errno = ENOENT;
#endif  /* _WIN32 */
    return -1;
}

#if defined(__human68k__) || defined(__DJGPP__) || defined(_WIN32)
static int
proc_spawn_v(argv, prog)
    char **argv;
    char *prog;
{
    char *extension;
    int status;

    if (!prog)
        prog = argv[0];
    security(prog);
    prog = dln_find_exe(prog, 0);
    if (!prog)
        return -1;

#if defined(__human68k__)
    if ((extension = strrchr(prog, '.')) != NULL && strcasecmp(extension, ".bat") == 0) {
        char **new_argv;
        char *p;
        int n;

        for (n = 0; argv[n]; n++)
            /* no-op */;
        new_argv = ALLOCA_N(char*, n + 2);
        for (; n > 0; n--)
            new_argv[n + 1] = argv[n];
        new_argv[1] = strcpy(ALLOCA_N(char, strlen(argv[0]) + 1), argv[0]);
        for (p = new_argv[1]; *p != '\0'; p++)
            if (*p == '/')
                *p = '\\';
        new_argv[0] = COMMAND;
        argv = new_argv;
        prog = dln_find_exe(argv[0], 0);
        if (!prog) {
            errno = ENOENT;
            return -1;
        }
    }
#endif
    before_exec();
#if defined(_WIN32)
    status = do_aspawn(P_WAIT, prog, argv);
#else
    status = spawnv(P_WAIT, prog, argv);
#endif
    after_exec();
    return status;
}

static int
proc_spawn_n(argc, argv, prog)
    int argc;
    VALUE *argv;
    VALUE prog;
{
    char **args;
    int i;

    args = ALLOCA_N(char*, argc + 1);
    for (i = 0; i < argc; i++) {
        SafeStringValue(argv[i]);
        args[i] = RSTRING(argv[i])->ptr;
    }
    if (prog)
        SafeStringValue(prog);
    args[i] = (char*) 0;
    if (args[0])
        return proc_spawn_v(args, prog ? RSTRING(prog)->ptr : 0);
    return -1;
}

#if !defined(_WIN32)
static int
proc_spawn(sv)
    VALUE sv;
{
    char *str;
    char *s, *t;
    char **argv, **a;
    int status;

    SafeStringValue(sv);
    str = s = RSTRING(sv)->ptr;
    for (s = str; *s; s++) {
        if (*s != ' ' && !ISALPHA(*s) && strchr("*?{}[]<>()~&|\\$;'`\"\n",*s)) {
            char *shell = dln_find_exe("sh", 0);
            before_exec();
            status = shell?spawnl(P_WAIT,shell,"sh","-c",str,(char*)NULL):system(str);
            after_exec();
            return status;
        }
    }
    a = argv = ALLOCA_N(char*, (s - str) / 2 + 2);
    s = ALLOCA_N(char, s - str + 1);
    strcpy(s, str);
    if (*a++ = strtok(s, " \t")) {
        while (t = strtok(NULL, " \t"))
            *a++ = t;
        *a = NULL;
    }
    return argv[0] ? proc_spawn_v(argv, 0) : -1;
}
#endif
#endif

/*
 *  call-seq:
 *     exec(command [, arg, ...])
 *
 *  Replaces the current process by running the given external _command_.
 *  If +exec+ is given a single argument, that argument is
 *  taken as a line that is subject to shell expansion before being
 *  executed. If multiple arguments are given, the second and subsequent
 *  arguments are passed as parameters to _command_ with no shell
 *  expansion. If the first argument is a two-element array, the first
 *  element is the command to be executed, and the second argument is
 *  used as the <code>argv[0]</code> value, which may show up in process
 *  listings. In MSDOS environments, the command is executed in a
 *  subshell; otherwise, one of the <code>exec(2)</code> system calls is
 *  used, so the running command may inherit some of the environment of
 *  the original program (including open file descriptors).
 *
 *     exec "echo *"       # echoes list of files in current directory
 *     # never get here
 *
 *
 *     exec "echo", "*"    # echoes an asterisk
 *     # never get here
 */

VALUE
rb_f_exec(argc, argv)
    int argc;
    VALUE *argv;
{
    VALUE prog = 0;
    VALUE tmp;

    if (argc == 0) {
        rb_raise(rb_eArgError, "wrong number of arguments");
    }

    tmp = rb_check_array_type(argv[0]);
    if (!NIL_P(tmp)) {
        if (RARRAY(tmp)->len != 2) {
            rb_raise(rb_eArgError, "wrong first argument");
        }
        prog = RARRAY(tmp)->ptr[0];
        argv[0] = RARRAY(tmp)->ptr[1];
        SafeStringValue(prog);
    }
    if (argc == 1 && prog == 0) {
        VALUE cmd = argv[0];

        SafeStringValue(cmd);
        rb_proc_exec(RSTRING(cmd)->ptr);
    }
    else {
        proc_exec_n(argc, argv, prog);
    }
    rb_sys_fail(RSTRING(argv[0])->ptr);
    return Qnil;                /* dummy */
}


/*
 *  call-seq:
 *     Kernel.fork  [{ block }]   => fixnum or nil
 *     Process.fork [{ block }]   => fixnum or nil
 *
 *  Creates a subprocess. If a block is specified, that block is run
 *  in the subprocess, and the subprocess terminates with a status of
 *  zero. Otherwise, the +fork+ call returns twice, once in
 *  the parent, returning the process ID of the child, and once in
 *  the child, returning _nil_. The child process can exit using
 *  <code>Kernel.exit!</code> to avoid running any
 *  <code>at_exit</code> functions. The parent process should
 *  use <code>Process.wait</code> to collect the termination statuses
 *  of its children or use <code>Process.detach</code> to register
 *  disinterest in their status; otherwise, the operating system
 *  may accumulate zombie processes.
 *
 *  The thread calling fork is the only thread in the created child process.
 *  fork doesn't copy other threads.
 */

static VALUE
rb_f_fork(obj)
    VALUE obj;
{
#if !defined(__human68k__) && !defined(_WIN32) && !defined(__MACOS__) && !defined(__EMX__) && !defined(__VMS)
    int pid;

    rb_secure(2);

#ifndef __VMS
    fflush(stdout);
    fflush(stderr);
#endif

    switch (pid = fork()) {
      case 0:
#ifdef linux
        after_exec();
#endif
        rb_thread_atfork();
        if (rb_block_given_p()) {
            int status;

            rb_protect(rb_yield, Qundef, &status);
            ruby_stop(status);
        }
        return Qnil;

      case -1:
        rb_sys_fail("fork(2)");
        return Qnil;

      default:
        return INT2FIX(pid);
    }
#else
    rb_notimplement();
#endif
}


/*
 *  call-seq:
 *     Process.exit!(fixnum=-1)
 *
 *  Exits the process immediately. No exit handlers are
 *  run. <em>fixnum</em> is returned to the underlying system as the
 *  exit status.
 *
 *     Process.exit!(0)
 */

static VALUE
rb_f_exit_bang(argc, argv, obj)
    int argc;
    VALUE *argv;
    VALUE obj;
{
    VALUE status;
    int istatus;

    rb_secure(4);
    if (rb_scan_args(argc, argv, "01", &status) == 1) {
        switch (status) {
          case Qtrue:
            istatus = EXIT_SUCCESS;
            break;
          case Qfalse:
            istatus = EXIT_FAILURE;
            break;
          default:
            istatus = NUM2INT(status);
            break;
        }
    }
    else {
        istatus = EXIT_FAILURE;
    }
    _exit(istatus);

    return Qnil;                /* not reached */
}

#if defined(sun)
#define signal(a,b) sigset(a,b)
#endif

void
rb_syswait(pid)
    int pid;
{
    static int overriding;
#ifdef SIGHUP
    RETSIGTYPE (*hfunc)(int);
#endif
#ifdef SIGQUIT
    RETSIGTYPE (*qfunc)(int);
#endif
    RETSIGTYPE (*ifunc)(int);
    int status;
    int i, hooked = Qfalse;

    if (!overriding) {
#ifdef SIGHUP
        hfunc = signal(SIGHUP, SIG_IGN);
#endif
#ifdef SIGQUIT
        qfunc = signal(SIGQUIT, SIG_IGN);
#endif
        ifunc = signal(SIGINT, SIG_IGN);
        overriding = Qtrue;
        hooked = Qtrue;
    }

    do {
        i = rb_waitpid(pid, &status, 0);
    } while (i == -1 && errno == EINTR);

    if (hooked) {
#ifdef SIGHUP
        signal(SIGHUP, hfunc);
#endif
#ifdef SIGQUIT
        signal(SIGQUIT, qfunc);
#endif
        signal(SIGINT, ifunc);
        overriding = Qfalse;
    }
}

/*
 *  call-seq:
 *     system(cmd [, arg, ...])    => true or false
 *
 *  Executes _cmd_ in a subshell, returning +true+ if
 *  the command was found and ran successfully, +false+
 *  otherwise. An error status is available in <code>$?</code>. The
 *  arguments are processed in the same way as for
 *  <code>Kernel::exec</code>.
 *
 *     system("echo *")
 *     system("echo", "*")
 *
 *  <em>produces:</em>
 *
 *     config.h main.rb
 *     *
 */

static VALUE
rb_f_system(argc, argv)
    int argc;
    VALUE *argv;
{
    int status;
#if defined(__EMX__)
    VALUE cmd;

    fflush(stdout);
    fflush(stderr);
    if (argc == 0) {
        rb_last_status = Qnil;
        rb_raise(rb_eArgError, "wrong number of arguments");
    }

    if (TYPE(argv[0]) == T_ARRAY) {
        if (RARRAY(argv[0])->len != 2) {
            rb_raise(rb_eArgError, "wrong first argument");
        }
        argv[0] = RARRAY(argv[0])->ptr[0];
    }
    cmd = rb_ary_join(rb_ary_new4(argc, argv), rb_str_new2(" "));

    SafeStringValue(cmd);
    status = do_spawn(RSTRING(cmd)->ptr);
    last_status_set(status, 0);
#elif defined(__human68k__) || defined(__DJGPP__) || defined(_WIN32)
    volatile VALUE prog = 0;

    fflush(stdout);
    fflush(stderr);
    if (argc == 0) {
        rb_last_status = Qnil;
        rb_raise(rb_eArgError, "wrong number of arguments");
    }

    if (TYPE(argv[0]) == T_ARRAY) {
        if (RARRAY(argv[0])->len != 2) {
            rb_raise(rb_eArgError, "wrong first argument");
        }
        prog = RARRAY(argv[0])->ptr[0];
        argv[0] = RARRAY(argv[0])->ptr[1];
    }

    if (argc == 1 && prog == 0) {
#if defined(_WIN32)
        SafeStringValue(argv[0]);
        status = do_spawn(P_WAIT, RSTRING(argv[0])->ptr);
#else
        status = proc_spawn(argv[0]);
#endif
    }
    else {
        status = proc_spawn_n(argc, argv, prog);
    }
#if !defined(_WIN32)
    last_status_set(status == -1 ? 127 : status, 0);
#endif
#elif defined(__VMS)
    VALUE cmd;

    if (argc == 0) {
        rb_last_status = Qnil;
        rb_raise(rb_eArgError, "wrong number of arguments");
    }

    if (TYPE(argv[0]) == T_ARRAY) {
        if (RARRAY(argv[0])->len != 2) {
            rb_raise(rb_eArgError, "wrong first argument");
        }
        argv[0] = RARRAY(argv[0])->ptr[0];
    }
    cmd = rb_ary_join(rb_ary_new4(argc, argv), rb_str_new2(" "));

    SafeStringValue(cmd);
    status = system(RSTRING(cmd)->ptr);
    last_status_set((status & 0xff) << 8, 0);
#else
    volatile VALUE prog = 0;
    int pid;
    int i;

    fflush(stdout);
    fflush(stderr);
    if (argc == 0) {
        rb_last_status = Qnil;
        rb_raise(rb_eArgError, "wrong number of arguments");
    }

    if (TYPE(argv[0]) == T_ARRAY) {
        if (RARRAY(argv[0])->len != 2) {
            rb_raise(rb_eArgError, "wrong first argument");
        }
        prog = RARRAY(argv[0])->ptr[0];
        argv[0] = RARRAY(argv[0])->ptr[1];
    }

    if (prog) {
        SafeStringValue(prog);
    }
    for (i = 0; i < argc; i++) {
        SafeStringValue(argv[i]);
    }
  retry:
    switch (pid = fork()) {
      case 0:
        if (argc == 1 && prog == 0) {
            rb_proc_exec(RSTRING(argv[0])->ptr);
        }
        else {
            proc_exec_n(argc, argv, prog);
        }
        _exit(127);
        break;                  /* not reached */

      case -1:
        if (errno == EAGAIN) {
            rb_thread_sleep(1);
            goto retry;
        }
        rb_sys_fail(0);
        break;

      default:
        rb_syswait(pid);
    }

    status = NUM2INT(rb_last_status);
#endif

    if (status == EXIT_SUCCESS) return Qtrue;
    return Qfalse;
}

/*
 *  call-seq:
 *     sleep([duration])    => fixnum
 *
 *  Suspends the current thread for _duration_ seconds (which may be
 *  any number, including a +Float+ with fractional seconds). Returns the actual
 *  number of seconds slept (rounded), which may be less than that asked
 *  for if the thread was interrupted by a +SIGALRM+, or if
 *  another thread calls <code>Thread#run</code>. Zero arguments
 *  causes +sleep+ to sleep forever.
 *
 *     Time.new    #=> Wed Apr 09 08:56:32 CDT 2003
 *     sleep 1.2   #=> 1
 *     Time.new    #=> Wed Apr 09 08:56:33 CDT 2003
 *     sleep 1.9   #=> 2
 *     Time.new    #=> Wed Apr 09 08:56:35 CDT 2003
 */

static VALUE
rb_f_sleep(argc, argv)
    int argc;
    VALUE *argv;
{
    int beg, end;

    beg = time(0);
    if (argc == 0) {
        rb_thread_sleep_forever();
    }
    else if (argc == 1) {
        rb_thread_wait_for(rb_time_interval(argv[0]));
    }
    else {
        rb_raise(rb_eArgError, "wrong number of arguments");
    }

    end = time(0) - beg;

    return INT2FIX(end);
}


/*
 *  call-seq:
 *     Process.getpgrp   => integer
 *
 *  Returns the process group ID for this process. Not available on
 *  all platforms.
 *
 *     Process.getpgid(0)   #=> 25527
 *     Process.getpgrp      #=> 25527
 */

static VALUE
proc_getpgrp()
{
    int pgrp;

    rb_secure(2);
#if defined(HAVE_GETPGRP) && defined(GETPGRP_VOID)
    pgrp = getpgrp();
    if (pgrp < 0) rb_sys_fail(0);
    return INT2FIX(pgrp);
#else
# ifdef HAVE_GETPGID
    pgrp = getpgid(0);
    if (pgrp < 0) rb_sys_fail(0);
    return INT2FIX(pgrp);
# else
    rb_notimplement();
# endif
#endif
}


/*
 *  call-seq:
 *     Process.setpgrp   => 0
 *
 *  Equivalent to <code>setpgid(0,0)</code>. Not available on all
 *  platforms.
 */

static VALUE
proc_setpgrp()
{
    rb_secure(2);
  /* check for posix setpgid() first; this matches the posix */
  /* getpgrp() above.  It appears that configure will set SETPGRP_VOID */
  /* even though setpgrp(0,0) would be prefered. The posix call avoids */
  /* this confusion. */
#ifdef HAVE_SETPGID
    if (setpgid(0,0) < 0) rb_sys_fail(0);
#elif defined(HAVE_SETPGRP) && defined(SETPGRP_VOID)
    if (setpgrp() < 0) rb_sys_fail(0);
#else
    rb_notimplement();
#endif
    return INT2FIX(0);
}


/*
 *  call-seq:
 *     Process.getpgid(pid)   => integer
 *
 *  Returns the process group ID for the given process id. Not
 *  available on all platforms.
 *
 *     Process.getpgid(Process.ppid())   #=> 25527
 */

static VALUE
proc_getpgid(obj, pid)
    VALUE obj, pid;
{
#if defined(HAVE_GETPGID) && !defined(__CHECKER__)
    int i;

    rb_secure(2);
    i = getpgid(NUM2INT(pid));
    if (i < 0) rb_sys_fail(0);
    return INT2NUM(i);
#else
    rb_notimplement();
#endif
}


/*
 *  call-seq:
 *     Process.setpgid(pid, integer)   => 0
 *
 *  Sets the process group ID of _pid_ (0 indicates this
 *  process) to <em>integer</em>. Not available on all platforms.
 */

static VALUE
proc_setpgid(obj, pid, pgrp)
    VALUE obj, pid, pgrp;
{
#ifdef HAVE_SETPGID
    int ipid, ipgrp;

    rb_secure(2);
    ipid = NUM2INT(pid);
    ipgrp = NUM2INT(pgrp);

    if (setpgid(ipid, ipgrp) < 0) rb_sys_fail(0);
    return INT2FIX(0);
#else
    rb_notimplement();
#endif
}


/*
 *  call-seq:
 *     Process.setsid   => fixnum
 *
 *  Establishes this process as a new session and process group
 *  leader, with no controlling tty. Returns the session id. Not
 *  available on all platforms.
 *
 *     Process.setsid   #=> 27422
 */

static VALUE
proc_setsid()
{
#if defined(HAVE_SETSID)
    int pid;

    rb_secure(2);
    pid = setsid();
    if (pid < 0) rb_sys_fail(0);
    return INT2FIX(pid);
#elif defined(HAVE_SETPGRP) && defined(TIOCNOTTY)
  rb_pid_t pid;
  int ret;

  rb_secure(2);
  pid = getpid();
#if defined(SETPGRP_VOID)
  ret = setpgrp();
  /* If `pid_t setpgrp(void)' is equivalent to setsid(),
     `ret' will be the same value as `pid', and following open() will fail.
     In Linux, `int setpgrp(void)' is equivalent to setpgid(0, 0). */
#else
  ret = setpgrp(0, pid);
#endif
  if (ret == -1) rb_sys_fail(0);

  if ((fd = open("/dev/tty", O_RDWR)) >= 0) {
    ioctl(fd, TIOCNOTTY, NULL);
    close(fd);
  }
  return INT2FIX(pid);
#else
    rb_notimplement();
#endif
}


/*
 *  call-seq:
 *     Process.getpriority(kind, integer)   => fixnum
 *
 *  Gets the scheduling priority for specified process, process group,
 *  or user. <em>kind</em> indicates the kind of entity to find: one
 *  of <code>Process::PRIO_PGRP</code>,
 *  <code>Process::PRIO_USER</code>, or
 *  <code>Process::PRIO_PROCESS</code>. _integer_ is an id
 *  indicating the particular process, process group, or user (an id
 *  of 0 means _current_). Lower priorities are more favorable
 *  for scheduling. Not available on all platforms.
 *
 *     Process.getpriority(Process::PRIO_USER, 0)      #=> 19
 *     Process.getpriority(Process::PRIO_PROCESS, 0)   #=> 19
 */

static VALUE
proc_getpriority(obj, which, who)
    VALUE obj, which, who;
{
#ifdef HAVE_GETPRIORITY
    int prio, iwhich, iwho;

    rb_secure(2);
    iwhich = NUM2INT(which);
    iwho   = NUM2INT(who);

    errno = 0;
    prio = getpriority(iwhich, iwho);
    if (errno) rb_sys_fail(0);
    return INT2FIX(prio);
#else
    rb_notimplement();
#endif
}


/*
 *  call-seq:
 *     Process.setpriority(kind, integer, priority)   => 0
 *
 *  See <code>Process#getpriority</code>.
 *
 *     Process.setpriority(Process::PRIO_USER, 0, 19)      #=> 0
 *     Process.setpriority(Process::PRIO_PROCESS, 0, 19)   #=> 0
 *     Process.getpriority(Process::PRIO_USER, 0)          #=> 19
 *     Process.getpriority(Process::PRIO_PROCESS, 0)       #=> 19
 */

static VALUE
proc_setpriority(obj, which, who, prio)
    VALUE obj, which, who, prio;
{
#ifdef HAVE_GETPRIORITY
    int iwhich, iwho, iprio;

    rb_secure(2);
    iwhich = NUM2INT(which);
    iwho   = NUM2INT(who);
    iprio  = NUM2INT(prio);

    if (setpriority(iwhich, iwho, iprio) < 0)
        rb_sys_fail(0);
    return INT2FIX(0);
#else
    rb_notimplement();
#endif
}

static int under_uid_switch = 0;
static void
check_uid_switch()
{
    rb_secure(2);
    if (under_uid_switch) {
        rb_raise(rb_eRuntimeError, "can't handle UID while evaluating block given to Process::UID.switch method");
    }
}

static int under_gid_switch = 0;
static void