BUILD.txt


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Very Quick Guide to build sssd components
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Use the following instructions to build the libraries and the binaries.

External library requirements:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
sssd depends on 4 libraries originated in the samba project:
talloc, tdb, tevent, ldb

They are now available in major distribution development branches.

If you want to build them from source download them from the following links:
http://samba.org/ftp/talloc/
http://samba.org/ftp/tdb/
http://samba.org/ftp/tevent/
http://samba.org/ftp/ldb/

Additionally the ding-libs are needed. These used to be included in the sssd
release but are now a separate project. The lastest ding-libs release can be
downloaded from https://fedorahosted.org/sssd/wiki/Releases#DING-LIBSReleases .

To install all of the dependencies in Fedora before building sssd:
yum install openldap-devel gettext libtool pcre-devel c-ares-devel \
    dbus-devel libxslt docbook-style-xsl krb5-devel nspr-devel \
    libxml2 pam-devel nss-devel libtevent python-devel \
    libtevent-devel libtdb libtdb-devel libtalloc libtalloc-devel \
    libldb libldb-devel cvs popt-devel c-ares-devel check-devel \
    doxygen libselinux-devel libsemanage-devel bind-utils libnl-devel \
    nscd gettext-devel

ding-libs are available in Fedora 14 and later version:
yum install  libcollection-devel  libdhash-devel  libini_config-devel \
     libpath_utils-devel  libref_array-devel

Some features, notably password caching, require the presence of a crypto
library. The default, tested by SSSD upstream, is Mozilla NSS. An alternative
crypto library can be selected during configure time using the --with-crypto
switch. Please note that alternative crypto back ends may not provide all
features -  as of this writing, password obfuscation is only supported with the
NSS back end.

How to build:
~~~~~~~~~~~~~
From the root of the source, run:
autoreconf -i -f && \
./configure && \
make

Optionally, parallel builds are possible with:
autoreconf -i -f && \
mkdir parallelbuilddir && cd parallelbuilddir && \
../configure && \
make

Now you have to copy libnss_sss* into /lib (or /lib64) and add the 'sss' target
to nsswitch.conf passwd database

For pam copy pam_sss.so into /lib/security (or /lib64/security) and add
pam_sss.so to your pam configuration. To use the pam_test_client from
sss_client create the following file:

/etc/pam.d/sss_test:
auth     required pam_sss.so
account  required pam_sss.so
password required pam_sss.so
session  required pam_sss.so

Now you can call pam_test_client:
./pam_test_client [auth|chau|acct|setc|open|clos] username@domain

~~~~~
Simo and Steve (Last updated for 1.5.2)
/**********************************************************************

  process.c -

  $Author$
  created at: Tue Aug 10 14:30:50 JST 1993

  Copyright (C) 1993-2007 Yukihiro Matsumoto
  Copyright (C) 2000  Network Applied Communication Laboratory, Inc.
  Copyright (C) 2000  Information-technology Promotion Agency, Japan

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

#include "ruby/ruby.h"
#include "ruby/io.h"
#include "ruby/util.h"
#include "vm_core.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 HAVE_FCNTL_H
#include <fcntl.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_SYS_RESOURCE_H
# include <sys/resource.h>
#endif
#ifdef HAVE_SYS_PARAM_H
# include <sys/param.h>
#endif
#ifndef MAXPATHLEN
# define MAXPATHLEN 1024
#endif
#include "ruby/st.h"

#ifdef __EMX__
#undef HAVE_GETPGRP
#endif

#include <sys/stat.h>

#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 rb_cProcessTms;
#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

#ifdef BROKEN_SETREUID
#define setreuid ruby_setreuid
#endif
#ifdef BROKEN_SETREGID
#define setregid ruby_setregid
#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

#if SIZEOF_RLIM_T == SIZEOF_INT
# define RLIM2NUM(v) UINT2NUM(v)
# define NUM2RLIM(v) NUM2UINT(v)
#elif SIZEOF_RLIM_T == SIZEOF_LONG
# define RLIM2NUM(v) ULONG2NUM(v)
# define NUM2RLIM(v) NUM2ULONG(v)
#elif SIZEOF_RLIM_T == SIZEOF_LONG_LONG
# define RLIM2NUM(v) ULL2NUM(v)
# define NUM2RLIM(v) NUM2ULL(v)
#endif

#define preserving_errno(stmts) \
	do {int saved_errno = errno; stmts; errno = saved_errno;} while (0)


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

static VALUE
get_pid(void)
{
    rb_secure(2);
    return PIDT2NUM(getpid());
}


/*
 *  call-seq:
 *     Process.ppid   => fixnum
 *
 *  Returns the process id of the parent of this process. Returns
 *  untrustworthy value on Win32/64. 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(void)
{
    rb_secure(2);
    return PIDT2NUM(getppid());
}


/*********************************************************************
 *
 * 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_cProcessStatus;

VALUE
rb_last_status_get(void)
{
    return GET_THREAD()->last_status;
}

void
rb_last_status_set(int status, rb_pid_t pid)
{
    rb_thread_t *th = GET_THREAD();
    th->last_status = rb_obj_alloc(rb_cProcessStatus);
    rb_iv_set(th->last_status, "status", INT2FIX(status));
    rb_iv_set(th->last_status, "pid", PIDT2NUM(pid));
}

static void
rb_last_status_clear(void)
{
    GET_THREAD()->last_status = Qnil;
}

/*
 *  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(VALUE st)
{
    return rb_iv_get(st, "status");
}

#define PST2INT(st) NUM2INT(pst_to_i(st))

/*
 *  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(VALUE st)
{
    return rb_attr_get(st, rb_intern("pid"));
}

static void
pst_message(VALUE str, rb_pid_t pid, int status)
{
    rb_str_catf(str, "pid %ld", (long)pid);
    if (WIFSTOPPED(status)) {
	int stopsig = WSTOPSIG(status);
	const char *signame = ruby_signal_name(stopsig);
	if (signame) {
	    rb_str_catf(str, " stopped SIG%s (signal %d)", signame, stopsig);
	}
	else {
	    rb_str_catf(str, " stopped signal %d", stopsig);
	}
    }
    if (WIFSIGNALED(status)) {
	int termsig = WTERMSIG(status);
	const char *signame = ruby_signal_name(termsig);
	if (signame) {
	    rb_str_catf(str, " SIG%s (signal %d)", signame, termsig);
	}
	else {
	    rb_str_catf(str, " signal %d", termsig);
	}
    }
    if (WIFEXITED(status)) {
	rb_str_catf(str, " exit %d", WEXITSTATUS(status));
    }
#ifdef WCOREDUMP
    if (WCOREDUMP(status)) {
	rb_str_cat2(str, " (core dumped)");
    }
#endif
}


/*
 *  call-seq:
 *     stat.to_s   => string
 *
 *  Show pid and exit status as a string.
 */

static VALUE
pst_to_s(VALUE st)
{
    rb_pid_t pid;
    int status;
    VALUE str;

    pid = NUM2PIDT(pst_pid(st));
    status = PST2INT(st);

    str = rb_str_buf_new(0);
    pst_message(str, pid, status);
    return str;
}


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

static VALUE
pst_inspect(VALUE st)
{
    rb_pid_t pid;
    int status;
    VALUE vpid, str;

    vpid = pst_pid(st);
    if (NIL_P(vpid)) {
        return rb_sprintf("#<%s: uninitialized>", rb_class2name(CLASS_OF(st)));
    }
    pid = NUM2PIDT(vpid);
    status = PST2INT(st);

    str = rb_sprintf("#<%s: ", rb_class2name(CLASS_OF(st)));
    pst_message(str, pid, status);
    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(VALUE st1, VALUE 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(VALUE st1, VALUE st2)
{
    int status = PST2INT(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(VALUE st1, VALUE st2)
{
    int status = PST2INT(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(VALUE st)
{
    int status = PST2INT(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(VALUE st)
{
    int status = PST2INT(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(VALUE st)
{
    int status = PST2INT(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(VALUE st)
{
    int status = PST2INT(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(VALUE st)
{
    int status = PST2INT(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(VALUE st)
{
    int status = PST2INT(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(VALUE st)
{
    int status = PST2INT(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(VALUE st)
{
#ifdef WCOREDUMP
    int status = PST2INT(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;

struct wait_data {
    rb_pid_t pid;
    int status;
};

static int
wait_each(rb_pid_t pid, int 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(rb_pid_t pid, int status, VALUE ary)
{
    rb_last_status_set(status, pid);
    rb_ary_push(ary, rb_assoc_new(PIDT2NUM(pid), rb_last_status_get()));
    return ST_DELETE;
}
#else
struct waitpid_arg {
    rb_pid_t pid;
    int *st;
    int flags;
};
#endif

static VALUE
rb_waitpid_blocking(void *data)
{
    rb_pid_t result;
#ifndef NO_WAITPID
    struct waitpid_arg *arg = data;
#endif

#if defined NO_WAITPID
    result = wait(data);
#elif defined HAVE_WAITPID
    result = waitpid(arg->pid, arg->st, arg->flags);
#else  /* HAVE_WAIT4 */
    result = wait4(arg->pid, arg->st, arg->flags, NULL);
#endif

    return (VALUE)result;
}

rb_pid_t
rb_waitpid(rb_pid_t pid, int *st, int flags)
{
    rb_pid_t result;
#ifndef NO_WAITPID
    struct waitpid_arg arg;

  retry:
    arg.pid = pid;
    arg.st = st;
    arg.flags = flags;
    result = (rb_pid_t)rb_thread_blocking_region(rb_waitpid_blocking, &arg,
						 RUBY_UBF_PROCESS, 0);
    if (result < 0) {
	if (errno == EINTR) {
            RUBY_VM_CHECK_INTS();
            goto retry;
        }
	return (rb_pid_t)-1;
    }
#else  /* NO_WAITPID */
    if (pid_tbl) {
	st_data_t status, piddata = (st_data_t)pid;
	if (pid == (rb_pid_t)-1) {
	    struct wait_data data;
	    data.pid = (rb_pid_t)-1;
	    data.status = -1;
	    st_foreach(pid_tbl, wait_each, (st_data_t)&data);
	    if (data.status != -1) {
		rb_last_status_set(data.status, data.pid);
		return data.pid;
	    }
	}
	else if (st_delete(pid_tbl, &piddata, &status)) {
	    rb_last_status_set(*st = (int)status, pid);
	    return pid;
	}
    }

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

    for (;;) {
	result = (rb_pid_t)rb_thread_blocking_region(rb_waitpid_blocking,
						     st, RUBY_UBF_PROCESS, 0);
	if (result < 0) {
	    if (errno == EINTR) {
		rb_thread_schedule();
		continue;
	    }
	    return (rb_pid_t)-1;
	}
	if (result == pid || pid == (rb_pid_t)-1) {
	    break;
	}
	if (!pid_tbl)
	    pid_tbl = st_init_numtable();
	st_insert(pid_tbl, pid, (st_data_t)st);
	if (!rb_thread_alone()) rb_thread_schedule();
    }
#endif
    if (result > 0) {
	rb_last_status_set(*st, result);
    }
    return result;
}


/* [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                         #=> 2008-03-08 19:56:16 +0900
 *     waitpid(pid, Process::WNOHANG)   #=> nil
 *     Time.now                         #=> 2008-03-08 19:56:16 +0900
 *     waitpid(pid, 0)                  #=> 27440
 *     Time.now                         #=> 2008-03-08 19:56:19 +0900
 */

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

    rb_secure(2);
    flags = 0;
    if (argc == 0) {
	pid = -1;
    }
    else {
	rb_scan_args(argc, argv, "02", &vpid, &vflags);
	pid = NUM2PIDT(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) {
	rb_last_status_clear();
	return Qnil;
    }
    return PIDT2NUM(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(int argc, VALUE *argv)
{
    VALUE pid = proc_wait(argc, argv);
    if (NIL_P(pid)) return Qnil;
    return rb_assoc_new(pid, rb_last_status_get());
}


/*
 *  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(void)
{
    VALUE result;
    rb_pid_t pid;
    int status;

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

    for (pid = -1;;) {
#ifdef NO_WAITPID
	pid = wait(&status);
#else
	pid = rb_waitpid(-1, &status, 0);
#endif
	if (pid == -1) {
	    if (errno == ECHILD)
		break;
#ifdef NO_WAITPID
	    if (errno == EINTR) {
		rb_thread_schedule();
		continue;
	    }
#endif
	    rb_sys_fail(0);
	}
#ifdef NO_WAITPID
	rb_last_status_set(status, pid);
#endif
	rb_ary_push(result, rb_assoc_new(PIDT2NUM(pid), rb_last_status_get()));
    }
    return result;
}

static inline ID
id_pid(void)
{
    ID pid;
    CONST_ID(pid, "pid");
    return pid;
}

static VALUE
detach_process_pid(VALUE thread)
{
    return rb_thread_local_aref(thread, id_pid());
}

static VALUE
detach_process_watcher(void *arg)
{
    rb_pid_t cpid, pid = (rb_pid_t)(VALUE)arg;
    int status;

    while ((cpid = rb_waitpid(pid, &status, 0)) == 0) {
	/* wait while alive */
    }
    return rb_last_status_get();
}

VALUE
rb_detach_process(rb_pid_t pid)
{
    VALUE watcher = rb_thread_create(detach_process_watcher, (void*)(VALUE)pid);
    rb_thread_local_aset(watcher, id_pid(), PIDT2NUM(pid));
    rb_define_singleton_method(watcher, "pid", detach_process_pid, 0);
    return watcher;
}


/*
 *  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.
 *
 *  The waiting thread returns the exit status of the detached process
 *  when it terminates, so you can use <code>Thread#join</code> to
 *  know the result.  If specified _pid_ is not a valid child process
 *  ID, the thread returns +nil+ immediately.
 *
 *  The waiting thread has <code>pid</code> method which returns the pid.
 *
 *  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(NUM2PIDT(pid));
}

#ifndef HAVE_STRING_H
char *strtok();
#endif

void rb_thread_stop_timer_thread(void);
void rb_thread_start_timer_thread(void);
void rb_thread_reset_timer_thread(void);

static int forked_child = 0;

#define before_exec() \
    (rb_enable_interrupt(), (forked_child ? 0 : (rb_thread_stop_timer_thread(), 1)))
#define after_exec() \
  (rb_thread_reset_timer_thread(), rb_thread_start_timer_thread(), forked_child = 0, rb_disable_interrupt())
#define before_fork() before_exec()
#define after_fork() (GET_THREAD()->thrown_errinfo = 0, after_exec())

#include "dln.h"

static void
security(const 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(char **argv, const char *prog)
{
    char fbuf[MAXPATHLEN];

    if (!prog)
	prog = argv[0];
    prog = dln_find_exe_r(prog, 0, fbuf, sizeof(fbuf));
    if (!prog) {
	errno = ENOENT;
	return -1;
    }

#if defined(__EMX__) || defined(OS2)
    {
#define COMMAND "cmd.exe"
	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_r(argv[0], 0, fbuf, sizeof(fbuf));
	    if (!prog) {
		errno = ENOENT;
		return -1;
	    }
	}
    }
#endif /* __EMX__ */
    before_exec();
    execv(prog, argv);
    preserving_errno(after_exec());
    return -1;
}

int
rb_proc_exec_n(int argc, VALUE *argv, const char *prog)
{
    char **args;
    int i;

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

int
rb_proc_exec(const char *str)
{
#ifndef _WIN32
    const char *s = str;
    char *ss, *t;
    char **argv, **a;
#endif

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

#ifdef _WIN32
    before_exec();
    rb_w32_spawn(P_OVERLAY, (char *)str, 0);
    after_exec();
#else
    for (s=str; *s; s++) {
	if (ISSPACE(*s)) {
	    const char *p, *nl = NULL;
	    for (p = s; ISSPACE(*p); p++) {
		if (*p == '\n') nl = p;
	    }
	    if (!*p) break;
	    if (nl) s = nl;
	}
	if (*s != ' ' && !ISALPHA(*s) && strchr("*?{}[]<>()~&|\\$;'`\"\n",*s)) {
#if defined(__CYGWIN32__) || defined(__EMX__)
	    char fbuf[MAXPATHLEN];
	    char *shell = dln_find_exe_r("sh", 0, fbuf, sizeof(fbuf));
	    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);
	    preserving_errno(after_exec());
#endif
	    return -1;
	}
    }
    a = argv = ALLOCA_N(char*, (s-str)/2+2);
    ss = ALLOCA_N(char, s-str+1);
    memcpy(ss, str, s-str);
    ss[s-str] = '\0';
    if ((*a++ = strtok(ss, " \t")) != 0) {
	while ((t = strtok(NULL, " \t")) != 0) {
	    *a++ = t;
	}
	*a = NULL;
    }
    if (argv[0]) {
	return proc_exec_v(argv, 0);
    }
    errno = ENOENT;
#endif	/* _WIN32 */
    return -1;
}

#if defined(_WIN32)
#define HAVE_SPAWNV 1
#endif

#if !defined(HAVE_FORK) && defined(HAVE_SPAWNV)
#if defined(_WIN32)
#define proc_spawn_v(argv, prog) rb_w32_aspawn(P_NOWAIT, prog, argv)
#else
static rb_pid_t
proc_spawn_v(char **argv, char *prog)
{
    char fbuf[MAXPATHLEN];
    rb_pid_t status;

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

    before_exec();
    status = spawnv(P_WAIT, prog, argv);
    rb_last_status_set(status == -1 ? 127 : status, 0);
    after_exec();
    return status;
}
#endif

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

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

#if defined(_WIN32)
#define proc_spawn(str) rb_w32_spawn(P_NOWAIT, str, 0)
#else
static rb_pid_t
proc_spawn(char *str)
{
    char fbuf[MAXPATHLEN];
    char *s, *t;
    char **argv, **a;
    rb_pid_t status;

    for (s = str; *s; s++) {
	if (*s != ' ' && !ISALPHA(*s) && strchr("*?{}[]<>()~&|\\$;'`\"\n",*s)) {
	    char *shell = dln_find_exe_r("sh", 0, fbuf, sizeof(fbuf));
	    before_exec();
	    status = shell?spawnl(P_WAIT,shell,"sh","-c",str,(char*)NULL):system(str);
	    rb_last_status_set(status == -1 ? 127 : status, 0);
	    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

static VALUE
hide_obj(VALUE obj)
{
    RBASIC(obj)->klass = 0;
    return obj;
}

enum {
    EXEC_OPTION_PGROUP,
    EXEC_OPTION_RLIMIT,
    EXEC_OPTION_UNSETENV_OTHERS,
    EXEC_OPTION_ENV,
    EXEC_OPTION_CHDIR,
    EXEC_OPTION_UMASK,
    EXEC_OPTION_DUP2,
    EXEC_OPTION_CLOSE,
    EXEC_OPTION_OPEN,
    EXEC_OPTION_DUP2_CHILD,
    EXEC_OPTION_CLOSE_OTHERS
};

static VALUE
check_exec_redirect_fd(VALUE v)
{
    VALUE tmp;
    int fd;
    if (FIXNUM_P(v)) {
        fd = FIX2INT(v);
    }
    else if (SYMBOL_P(v)) {
        ID id = SYM2ID(v);
        if (id == rb_intern("in"))
            fd = 0;
        else if (id == rb_intern("out"))
            fd = 1;
        else if (id == rb_intern("err"))
            fd = 2;
        else
            goto wrong;
    }
    else if (!NIL_P(tmp = rb_check_convert_type(v, T_FILE, "IO", "to_io"))) {
        rb_io_t *fptr;
        GetOpenFile(tmp, fptr);
        if (fptr->tied_io_for_writing)
            rb_raise(rb_eArgError, "duplex IO redirection");
        fd = fptr->fd;
    }
    else {
        rb_raise(rb_eArgError, "wrong exec redirect");
    }
    if (fd < 0) {
      wrong:
        rb_raise(rb_eArgError, "negative file descriptor");
    }
    return INT2FIX(fd);
}

static void
check_exec_redirect(VALUE key, VALUE val, VALUE options)
{
    int index;
    VALUE ary, param;
    VALUE path, flags, perm;
    ID id;

    switch (TYPE(val)) {
      case T_SYMBOL:
        id = SYM2ID(val);
        if (id == rb_intern("close")) {
            index = EXEC_OPTION_CLOSE;
            param = Qnil;
        }
        else if (id == rb_intern("in")) {
            index = EXEC_OPTION_DUP2;
            param = INT2FIX(0);
        }
        else if (id == rb_intern("out")) {
            index = EXEC_OPTION_DUP2;
            param = INT2FIX(1);
        }
        else if (id == rb_intern("err")) {
            index = EXEC_OPTION_DUP2;
            param = INT2FIX(2);
        }
        else {
            rb_raise(rb_eArgError, "wrong exec redirect symbol: %s",
                                   rb_id2name(id));
        }
        break;

      case T_FILE:
        val = check_exec_redirect_fd(val);
        /* fall through */
      case T_FIXNUM:
        index = EXEC_OPTION_DUP2;
        param = val;
        break;

      case T_ARRAY:
        path = rb_ary_entry(val, 0);
        if (RARRAY_LEN(val) == 2 && SYMBOL_P(path) &&
            SYM2ID(path) == rb_intern("child")) {
            index = EXEC_OPTION_DUP2_CHILD;
            param = check_exec_redirect_fd(rb_ary_entry(val, 1));
        }
        else {
            index = EXEC_OPTION_OPEN;
            FilePathValue(path);
            flags = rb_ary_entry(val, 1);
            if (NIL_P(flags))
                flags = INT2NUM(O_RDONLY);
            else if (TYPE(flags) == T_STRING)
                flags = INT2NUM(rb_io_modestr_oflags(StringValueCStr(flags)));
            else
                flags = rb_to_int(flags);
            perm = rb_ary_entry(val, 2);
            perm = NIL_P(perm) ? INT2FIX(0644) : rb_to_int(perm);
            param = hide_obj(rb_ary_new3(3, hide_obj(rb_str_dup(path)),
                                            flags, perm));
        }
        break;

      case T_STRING:
        index = EXEC_OPTION_OPEN;
        path = val;
        FilePathValue(path);
        if (TYPE(key) == T_FILE)
            key = check_exec_redirect_fd(key);
        if (FIXNUM_P(key) && (FIX2INT(key) == 1 || FIX2INT(key) == 2))
            flags = INT2NUM(O_WRONLY|O_CREAT|O_TRUNC);
        else
            flags = INT2NUM(O_RDONLY);
        perm = INT2FIX(0644);
        param = hide_obj(rb_ary_new3(3, hide_obj(rb_str_dup(path)),
                                        flags, perm));
        break;

      default:
        rb_raise(rb_eArgError, "wrong exec redirect action");
    }

    ary = rb_ary_entry(options, index);
    if (NIL_P(ary)) {
        ary = hide_obj(rb_ary_new());
        rb_ary_store(options, index, ary);
    }
    if (TYPE(key) != T_ARRAY) {
        VALUE fd = check_exec_redirect_fd(key);
        rb_ary_push(ary, hide_obj(rb_assoc_new(fd, param)));
    }
    else {
        int i, n=0;
        for (i = 0 ; i < RARRAY_LEN(key); i++) {
            VALUE v = RARRAY_PTR(key)[i];
            VALUE fd = check_exec_redirect_fd(v);
            rb_ary_push(ary, hide_obj(rb_assoc_new(fd, param)));
            n++;
        }
    }
}

#ifdef RLIM2NUM
static int rlimit_type_by_lname(const char *name);
#endif

int
rb_exec_arg_addopt(struct rb_exec_arg *e, VALUE key, VALUE val)
{
    VALUE options = e->options;
    ID id;
#ifdef RLIM2NUM
    int rtype;
#endif

    rb_secure(2);

    switch (TYPE(key)) {
      case T_SYMBOL:
        id = SYM2ID(key);
#ifdef HAVE_SETPGID
        if (id == rb_intern("pgroup")) {
            if (!NIL_P(rb_ary_entry(options, EXEC_OPTION_PGROUP))) {
                rb_raise(rb_eArgError, "pgroup option specified twice");
            }
            if (!RTEST(val))
                val = Qfalse;
            else if (val == Qtrue)
                val = INT2FIX(0);
            else {
                pid_t pgroup = NUM2PIDT(val);
                if (pgroup < 0) {
                    rb_raise(rb_eArgError, "negative process group ID : %ld", (long)pgroup);
                }
                val = PIDT2NUM(pgroup);
            }
            rb_ary_store(options, EXEC_OPTION_PGROUP, val);
        }
        else
#endif
#ifdef RLIM2NUM
        if (strncmp("rlimit_", rb_id2name(id), 7) == 0 &&
            (rtype = rlimit_type_by_lname(rb_id2name(id)+7)) != -1) {
            VALUE ary = rb_ary_entry(options, EXEC_OPTION_RLIMIT);
            VALUE tmp, softlim, hardlim;
            if (NIL_P(ary)) {
                ary = hide_obj(rb_ary_new());
                rb_ary_store(options, EXEC_OPTION_RLIMIT, ary);
            }
            tmp = rb_check_array_type(val);
            if (!NIL_P(tmp)) {
                if (RARRAY_LEN(tmp) == 1)
                    softlim = hardlim = rb_to_int(rb_ary_entry(tmp, 0));
                else if (RARRAY_LEN(tmp) == 2) {
                    softlim = rb_to_int(rb_ary_entry(tmp, 0));
                    hardlim = rb_to_int(rb_ary_entry(tmp, 1));
                }
                else {
                    rb_raise(rb_eArgError, "wrong exec rlimit option");
                }
            }
            else {
                softlim = hardlim = rb_to_int(val);
            }
            tmp = hide_obj(rb_ary_new3(3, INT2NUM(rtype), softlim, hardlim));
            rb_ary_push(ary, tmp);
        }
        else
#endif
        if (id == rb_intern("unsetenv_others")) {
            if (!NIL_P(rb_ary_entry(options, EXEC_OPTION_UNSETENV_OTHERS))) {
                rb_raise(rb_eArgError, "unsetenv_others option specified twice");
            }
            val = RTEST(val) ? Qtrue : Qfalse;
            rb_ary_store(options, EXEC_OPTION_UNSETENV_OTHERS, val);
        }
        else if (id == rb_intern("chdir")) {
            if (!NIL_P(rb_ary_entry(options, EXEC_OPTION_CHDIR))) {
                rb_raise(rb_eArgError, "chdir option specified twice");
            }
            FilePathValue(val);
            rb_ary_store(options, EXEC_OPTION_CHDIR,
                                  hide_obj(rb_str_dup(val)));
        }
        else if (id == rb_intern("umask")) {
            mode_t cmask = NUM2LONG(val);
            if (!NIL_P(rb_ary_entry(options, EXEC_OPTION_UMASK))) {
                rb_raise(rb_eArgError, "umask option specified twice");
            }
            rb_ary_store(options, EXEC_OPTION_UMASK, LONG2NUM(cmask));
        }
        else if (id == rb_intern("close_others")) {
            if (!NIL_P(rb_ary_entry(options, EXEC_OPTION_CLOSE_OTHERS))) {
                rb_raise(rb_eArgError, "close_others option specified twice");
            }
            val = RTEST(val) ? Qtrue : Qfalse;
            rb_ary_store(options, EXEC_OPTION_CLOSE_OTHERS, val);
        }
        else if (id == rb_intern("in")) {
            key = INT2FIX(0);
            goto redirect;
        }
        else if (id == rb_intern("out")) {
            key = INT2FIX(1);
            goto redirect;
        }
        else if (id == rb_intern("err")) {
            key = INT2FIX(2);
            goto redirect;
        }
        else {
            rb_raise(rb_eArgError, "wrong exec option symbol: %s",
                                   rb_id2name(id));
        }
        break;

      case T_FIXNUM:
      case T_FILE:
      case T_ARRAY:
redirect:
        check_exec_redirect(key, val, options);
        break;

      default:
        rb_raise(rb_eArgError, "wrong exec option");
    }

    return ST_CONTINUE;
}

static int
check_exec_options_i(st_data_t st_key, st_data_t st_val, st_data_t arg)
{
    VALUE key = (VALUE)st_key;
    VALUE val = (VALUE)st_val;
    struct rb_exec_arg *e = (struct rb_exec_arg *)arg;
    return rb_exec_arg_addopt(e, key, val);
}

static VALUE
check_exec_fds(VALUE options)
{
    VALUE h = rb_hash_new();
    VALUE ary;
    int index, i;
    int maxhint = -1;

    for (index = EXEC_OPTION_DUP2; index <= EXEC_OPTION_DUP2_CHILD; index++) {
        ary = rb_ary_entry(options, index);
        if (NIL_P(ary))
            continue;
        for (i = 0; i < RARRAY_LEN(ary); i++) {
            VALUE elt = RARRAY_PTR(ary)[i];
            int fd = FIX2INT(RARRAY_PTR(elt)[0]);
            if (RTEST(rb_hash_lookup(h, INT2FIX(fd)))) {
                rb_raise(rb_eArgError, "fd %d specified twice", fd);
            }
            if (index == EXEC_OPTION_OPEN || index == EXEC_OPTION_DUP2)
                rb_hash_aset(h, INT2FIX(fd), Qtrue);
            else if (index == EXEC_OPTION_DUP2_CHILD)
                rb_hash_aset(h, INT2FIX(fd), RARRAY_PTR(elt)[1]);
            else /* index == EXEC_OPTION_CLOSE */
                rb_hash_aset(h, INT2FIX(fd), INT2FIX(-1));
            if (maxhint < fd)
                maxhint = fd;
            if (index == EXEC_OPTION_DUP2 || index == EXEC_OPTION_DUP2_CHILD) {
                fd = FIX2INT(RARRAY_PTR(elt)[1]);
                if (maxhint < fd)
                    maxhint = fd;
            }
        }
    }

    ary = rb_ary_entry(options, EXEC_OPTION_DUP2_CHILD);
    if (!NIL_P(ary)) {
        for (i = 0; i < RARRAY_LEN(ary); i++) {
            VALUE elt = RARRAY_PTR(ary)[i];
            int newfd = FIX2INT(RARRAY_PTR(elt)[0]);
            int oldfd = FIX2INT(RARRAY_PTR(elt)[1]);
            int lastfd = oldfd;
            VALUE val = rb_hash_lookup(h, INT2FIX(lastfd));
            long depth = 0;
            while (FIXNUM_P(val) && 0 <= FIX2INT(val)) {
                lastfd = FIX2INT(val);
                val = rb_hash_lookup(h, val);
                if (RARRAY_LEN(ary) < depth)
                    rb_raise(rb_eArgError, "cyclic child fd redirection from %d", oldfd);
                depth++;
            }
            if (val != Qtrue)
                rb_raise(rb_eArgError, "child fd %d is not redirected", oldfd);
            if (oldfd != lastfd) {
                VALUE val2;
                rb_ary_store(elt, 1, INT2FIX(lastfd));
                rb_hash_aset(h, INT2FIX(newfd), INT2FIX(lastfd));
                val = INT2FIX(oldfd);
                while (FIXNUM_P(val2 = rb_hash_lookup(h, val))) {
                    rb_hash_aset(h, val, INT2FIX(lastfd));
                    val = val2;
                }
            }
        }
    }

    if (rb_ary_entry(options, EXEC_OPTION_CLOSE_OTHERS) != Qfalse) {
        rb_ary_store(options, EXEC_OPTION_CLOSE_OTHERS, INT2FIX(maxhint));
    }
    return h;
}

static void
rb_check_exec_options(VALUE opthash, struct rb_exec_arg *e)
{
    if (RHASH_EMPTY_P(opthash))
        return;
    st_foreach(RHASH_TBL(opthash), check_exec_options_i, (st_data_t)e);
}

static int
check_exec_env_i(st_data_t st_key, st_data_t st_val, st_data_t arg)
{
    VALUE key = (VALUE)st_key;
    VALUE val = (VALUE)st_val;
    VALUE env = (VALUE)arg;
    char *k;

    k = StringValueCStr(key);
    if (strchr(k, '='))
        rb_raise(rb_eArgError, "environment name contains a equal : %s", k);

    if (!NIL_P(val))
        StringValueCStr(val);

    rb_ary_push(env, hide_obj(rb_assoc_new(key, val)));

    return ST_CONTINUE;
}

static VALUE
rb_check_exec_env(VALUE hash)
{
    VALUE env;

    env = hide_obj(rb_ary_new());
    st_foreach(RHASH_TBL(hash), check_exec_env_i, (st_data_t)env);

    return env;
}

static VALUE
rb_check_argv(int argc, VALUE *argv)
{
    VALUE tmp, prog;
    int i;
    const char *name = 0;

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

    prog = 0;
    tmp = rb_check_array_type(argv[0]);
    if (!NIL_P(tmp)) {
	if (RARRAY_LEN(tmp) != 2) {
	    rb_raise(rb_eArgError, "wrong first argument");
	}
	prog = RARRAY_PTR(tmp)[0];
	argv[0] = RARRAY_PTR(tmp)[1];
	SafeStringValue(prog);
	StringValueCStr(prog);
	prog = rb_str_new4(prog);
	name = RSTRING_PTR(prog);
    }
    for (i = 0; i < argc; i++) {
	SafeStringValue(argv[i]);
	argv[i] = rb_str_new4(argv[i]);
	StringValueCStr(argv[i]);
    }
    security(name ? name : RSTRING_PTR(argv[0]));
    return prog;
}

static VALUE
rb_exec_getargs(int *argc_p, VALUE **argv_p, int accept_shell, VALUE *env_ret, VALUE *opthash_ret, struct rb_exec_arg *e)
{
    VALUE hash, prog;

    if (0 < *argc_p) {
        hash = rb_check_convert_type((*argv_p)[*argc_p-1], T_HASH, "Hash", "to_hash");
        if (!NIL_P(hash)) {
            *opthash_ret = hash;
            (*argc_p)--;
        }
    }

    if (0 < *argc_p) {
        hash = rb_check_convert_type((*argv_p)[0], T_HASH, "Hash", "to_hash");
        if (!NIL_P(hash)) {
            *env_ret = hash;
            (*argc_p)--;
            (*argv_p)++;
        }
    }
    prog = rb_check_argv(*argc_p, *argv_p);
    if (!prog) {
        prog = (*argv_p)[0];
        if (accept_shell && *argc_p == 1) {
            *argc_p = 0;
            *argv_p = 0;
        }
    }
    return prog;
}

static void
rb_exec_fillarg(VALUE prog, int argc, VALUE *argv, VALUE env, VALUE opthash, struct rb_exec_arg *e)
{
    VALUE options;
    MEMZERO(e, struct rb_exec_arg, 1);
    options = hide_obj(rb_ary_new());
    e->options = options;

    if (!NIL_P(opthash)) {
        rb_check_exec_options(opthash, e);
    }
    if (!NIL_P(env)) {
        env = rb_check_exec_env(env);
        rb_ary_store(options, EXEC_OPTION_ENV, env);
    }

    e->argc = argc;
    e->argv = argv;
    e->prog = prog ? RSTRING_PTR(prog) : 0;
}

VALUE
rb_exec_arg_init(int argc, VALUE *argv, int accept_shell, struct rb_exec_arg *e)
{
    VALUE prog;
    VALUE env = Qnil, opthash = Qnil;
    prog = rb_exec_getargs(&argc, &argv, accept_shell, &env, &opthash, e);
    rb_exec_fillarg(prog, argc, argv, env, opthash, e);
    return prog;
}

void
rb_exec_arg_fixup(struct rb_exec_arg *e)
{
    e->redirect_fds = check_exec_fds(e->options);
}

/*
 *  call-seq:
 *     exec([env,] command... [,options])
 *
 *  Replaces the current process by running the given external _command_.
 *  _command..._ is one of following forms.
 *
 *    commandline                 : command line string which is passed to a shell
 *    cmdname, arg1, ...          : command name and one or more arguments (no shell)
 *    [cmdname, argv0], arg1, ... : command name, argv[0] and zero or more arguments (no shell)
 *
 *  If single string is given as the command,
 *  it is taken as a command line that is subject to shell expansion before being executed.
 *
 *  If two or more +string+ given,
 *  the first is taken as a command name and
 *  the rest are passed as parameters to command with no shell expansion.
 *
 *  If a two-element array at the beginning of the command,
 *  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 order to execute the command, 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).
 *  This behavior is modified by env and options.
 *  See <code>spawn</code> for details.
 *
 *  Raises SystemCallError if the command couldn't execute (typically
 *  <code>Errno::ENOENT</code> when it was not found).
 *
 *     exec "echo *"       # echoes list of files in current directory
 *     # never get here
 *
 *
 *     exec "echo", "*"    # echoes an asterisk
 *     # never get here
 */

VALUE
rb_f_exec(int argc, VALUE *argv)
{
    struct rb_exec_arg earg;
#define CHILD_ERRMSG_BUFLEN 80
    char errmsg[CHILD_ERRMSG_BUFLEN] = { '\0' };

    rb_exec_arg_init(argc, argv, Qtrue, &earg);
    if (NIL_P(rb_ary_entry(earg.options, EXEC_OPTION_CLOSE_OTHERS)))
        rb_exec_arg_addopt(&earg, ID2SYM(rb_intern("close_others")), Qfalse);
    rb_exec_arg_fixup(&earg);

    rb_exec_err(&earg, errmsg, sizeof(errmsg));
    if (errmsg[0])
        rb_sys_fail(errmsg);
    rb_sys_fail(earg.prog);
    return Qnil;		/* dummy */
}

#define ERRMSG(str) do { if (errmsg && 0 < errmsg_buflen) strlcpy(errmsg, (str), errmsg_buflen); } while (0)

/*#define DEBUG_REDIRECT*/
#if defined(DEBUG_REDIRECT)

#include <stdarg.h>

static void
ttyprintf(const char *fmt, ...)
{
    va_list ap;
    FILE *tty;
    int save = errno;
#ifdef _WIN32
    tty = fopen("con", "w");
#else
    tty = fopen("/dev/tty", "w");
#endif
    if (!tty)
        return;

    va_start(ap, fmt);
    vfprintf(tty, fmt, ap);
    va_end(ap);
    fclose(tty);
    errno = save;
}

static int
redirect_dup(int oldfd)
{
    int ret;
    ret = dup(oldfd);
    ttyprintf("dup(%d) => %d\n", oldfd, ret);
    return ret;
}

static int
redirect_dup2(int oldfd, int newfd)
{
    int ret;
    ret = dup2(oldfd, newfd);
    ttyprintf("dup2(%d, %d)\n", oldfd, newfd);
    return ret;
}

static int
redirect_close(int fd)
{
    int ret;
    ret = close(fd);
    ttyprintf("close(%d)\n", fd);
    return ret;
}

static int
redirect_open(const char *pathname, int flags, mode_t perm)
{
    int ret;
    ret = open(pathname, flags, perm);
    ttyprintf("open(\"%s\", 0x%x, 0%o) => %d\n", pathname, flags, perm, ret);
    return ret;
}

#else
#define redirect_dup(oldfd) dup(oldfd)
#define redirect_dup2(oldfd, newfd) dup2(oldfd, newfd)
#define redirect_close(fd) close(fd)
#define redirect_open(pathname, flags, perm) open(pathname, flags, perm)
#endif

static int
save_redirect_fd(int fd, VALUE save, char *errmsg, size_t errmsg_buflen)
{
    if (!NIL_P(save)) {
        VALUE newary;
        int save_fd = redirect_dup(fd);
        if (save_fd == -1) {
            ERRMSG("dup");
            return -1;
        }
        newary = rb_ary_entry(save, EXEC_OPTION_DUP2);
        if (NIL_P(newary)) {
            newary = hide_obj(rb_ary_new());
            rb_ary_store(save, EXEC_OPTION_DUP2, newary);
        }
        rb_ary_push(newary,
                    hide_obj(rb_assoc_new(INT2FIX(fd), INT2FIX(save_fd))));

        newary = rb_ary_entry(save, EXEC_OPTION_CLOSE);
        if (NIL_P(newary)) {
            newary = hide_obj(rb_ary_new());
            rb_ary_store(save, EXEC_OPTION_CLOSE, newary);
        }
        rb_ary_push(newary, hide_obj(rb_assoc_new(INT2FIX(save_fd), Qnil)));
    }

    return 0;
}

static VALUE
save_env_i(VALUE i, VALUE ary, int argc, VALUE *argv)
{
    rb_ary_push(ary, hide_obj(rb_ary_dup(argv[0])));
    return Qnil;
}

static void
save_env(VALUE save)
{
    if (!NIL_P(save) && NIL_P(rb_ary_entry(save, EXEC_OPTION_ENV))) {
        VALUE env = rb_const_get(rb_cObject, rb_intern("ENV"));
        if (RTEST(env)) {
            VALUE ary = hide_obj(rb_ary_new());
            rb_block_call(env, rb_intern("each"), 0, 0, save_env_i,
                          (VALUE)ary);
            rb_ary_store(save, EXEC_OPTION_ENV, ary);
        }
        rb_ary_store(save, EXEC_OPTION_UNSETENV_OTHERS, Qtrue);
    }
}

static int
intcmp(const void *a, const void *b)
{
    return *(int*)a - *(int*)b;
}

static int
intrcmp(const void *a, const void *b)
{
    return *(int*)b - *(int*)a;
}

static int
run_exec_dup2(VALUE ary, VALUE save, char *errmsg, size_t errmsg_buflen)
{
    long n, i;
    int ret;
    int extra_fd = -1;
    struct fd_pair {
        int oldfd;
        int newfd;
        int older_index;
        int num_newer;
    } *pairs = 0;

    n = RARRAY_LEN(ary);
    pairs = (struct fd_pair *)malloc(sizeof(struct fd_pair) * n);
    if (pairs == NULL) {
        ERRMSG("malloc");
        return -1;
    }

    /* initialize oldfd and newfd: O(n) */
    for (i = 0; i < n; i++) {
        VALUE elt = RARRAY_PTR(ary)[i];
        pairs[i].oldfd = FIX2INT(RARRAY_PTR(elt)[1]);
        pairs[i].newfd = FIX2INT(RARRAY_PTR(elt)[0]); /* unique */
        pairs[i].older_index = -1;
    }

    /* sort the table by oldfd: O(n log n) */
    if (!RTEST(save))
        qsort(pairs, n, sizeof(struct fd_pair), intcmp);
    else
        qsort(pairs, n, sizeof(struct fd_pair), intrcmp);

    /* initialize older_index and num_newer: O(n log n) */
    for (i = 0; i < n; i++) {
        int newfd = pairs[i].newfd;
        struct fd_pair key, *found;
        key.oldfd = newfd;
        found = bsearch(&key, pairs, n, sizeof(struct fd_pair), intcmp);
        pairs[i].num_newer = 0;
        if (found) {
            while (pairs < found && (found-1)->oldfd == newfd)
                found--;
            while (found < pairs+n && found->oldfd == newfd) {
                pairs[i].num_newer++;
                found->older_index = i;
                found++;
            }
        }
    }

    /* non-cyclic redirection: O(n) */
    for (i = 0; i < n; i++) {
        int j = i;
        while (j != -1 && pairs[j].oldfd != -1 && pairs[j].num_newer == 0) {
            if (save_redirect_fd(pairs[j].newfd, save, errmsg, errmsg_buflen) < 0)
                goto fail;
            ret = redirect_dup2(pairs[j].oldfd, pairs[j].newfd);
            if (ret == -1) {
                ERRMSG("dup2");
                goto fail;
            }
            pairs[j].oldfd = -1;
            j = pairs[j].older_index;
            if (j != -1)
                pairs[j].num_newer--;
        }
    }

    /* cyclic redirection: O(n) */
    for (i = 0; i < n; i++) {
        int j;
        if (pairs[i].oldfd == -1)
            continue;
        if (pairs[i].oldfd == pairs[i].newfd) { /* self cycle */
#ifdef F_GETFD
            int fd = pairs[i].oldfd;
            ret = fcntl(fd, F_GETFD);
            if (ret == -1) {
                ERRMSG("fcntl(F_GETFD)");
                goto fail;
            }
            if (ret & FD_CLOEXEC) {
                ret &= ~FD_CLOEXEC;
                ret = fcntl(fd, F_SETFD, ret);
                if (ret == -1) {
                    ERRMSG("fcntl(F_SETFD)");
                    goto fail;
                }
            }
#endif
            pairs[i].oldfd = -1;
            continue;
        }
        if (extra_fd == -1) {
            extra_fd = redirect_dup(pairs[i].oldfd);
            if (extra_fd == -1) {
                ERRMSG("dup");
                goto fail;
            }
        }
        else {
            ret = redirect_dup2(pairs[i].oldfd, extra_fd);
            if (ret == -1) {
                ERRMSG("dup2");
                goto fail;
            }
        }
        pairs[i].oldfd = extra_fd;
        j = pairs[i].older_index;
        pairs[i].older_index = -1;
        while (j != -1) {
            ret = redirect_dup2(pairs[j].oldfd, pairs[j].newfd);
            if (ret == -1) {
                ERRMSG("dup2");
                goto fail;
            }
            pairs[j].oldfd = -1;
            j = pairs[j].older_index;
        }
    }
    if (extra_fd != -1) {
        ret = redirect_close(extra_fd);
        if (ret == -1) {
            ERRMSG("close");
            goto fail;
        }
    }

    xfree(pairs);
    return 0;

  fail:
    xfree(pairs);
    return -1;
}

static int
run_exec_close(VALUE ary, char *errmsg, size_t errmsg_buflen)
{
    int i, ret;

    for (i = 0; i < RARRAY_LEN(ary); i++) {
        VALUE elt = RARRAY_PTR(ary)[i];
        int fd = FIX2INT(RARRAY_PTR(elt)[0]);
        ret = redirect_close(fd);
        if (ret == -1) {
            ERRMSG("close");
            return -1;
        }
    }
    return 0;
}

static int
run_exec_open(VALUE ary, VALUE save, char *errmsg, size_t errmsg_buflen)
{
    int i, ret;

    for (i = 0; i < RARRAY_LEN(ary);) {
        VALUE elt = RARRAY_PTR(ary)[i];
        int fd = FIX2INT(RARRAY_PTR(elt)[0]);
        VALUE param = RARRAY_PTR(elt)[1];
        char *path = RSTRING_PTR(RARRAY_PTR(param)[0]);
        int flags = NUM2INT(RARRAY_PTR(param)[1]);
        int perm = NUM2INT(RARRAY_PTR(param)[2]);
        int need_close = 1;
        int fd2 = redirect_open(path, flags, perm);
        if (fd2 == -1) {
            ERRMSG("open");
            return -1;
        }
        while (i < RARRAY_LEN(ary) &&
               (elt = RARRAY_PTR(ary)[i], RARRAY_PTR(elt)[1] == param)) {
            fd = FIX2INT(RARRAY_PTR(elt)[0]);
            if (fd == fd2) {
                need_close = 0;
            }
            else {
                if (save_redirect_fd(fd, save, errmsg, errmsg_buflen) < 0)
                    return -1;
                ret = redirect_dup2(fd2, fd);
                if (ret == -1) {
                    ERRMSG("dup2");
                    return -1;
                }
            }
            i++;
        }
        if (need_close) {
            ret = redirect_close(fd2);
            if (ret == -1) {
                ERRMSG("close");
                return -1;
            }
        }