improve system library.

git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@113 b08c6af1-5177-4d33-ba66-4b1c6b8b522a

C/c_interface.c

@@ -112,7 +112,7 @@ YapA(int i)
 X_API Bool 
 YapIsIntTerm(Term t)
 {
-  return (IsIntTerm(t) || IsLongIntTerm(t));
+  return (IsIntegerTerm(t));
 }
 
 X_API Bool 

C/iopreds.c

@@ -106,7 +106,11 @@ typedef struct
 	Int pos;
       } mem_string;
       struct {
+#if defined(__MINGW32__) || _MSC_VER
+	HANDLE hdl;
+#else
 	int fd;
+#endif
       } pipe;
 #if USE_SOCKET
       struct {
@@ -687,7 +691,17 @@ ConsolePipePutc (int sno, int ch)
       ch = '\n';
     }
 #endif
+#if _MSC_VER || defined(__MINGW32__) 
+  {
+    DWORD written;
+    if (WriteFile(s->u.pipe.hdl, &c, sizeof(c), &written, NULL) == FALSE) {
+      PlIOError (SYSTEM_ERROR,TermNil, "write to pipe returned error");
+      return(EOF);
+    }
+  }
+#else
   write(s->u.pipe.fd,  &c, sizeof(c));
+#endif
   count_output_char(ch,s,sno);
   return ((int) ch);
 }
@@ -703,7 +717,17 @@ PipePutc (int sno, int ch)
       ch = '\n';
     }
 #endif
+#if _MSC_VER || defined(__MINGW32__) 
+  {
+    DWORD written;
+    if (WriteFile(s->u.pipe.hdl, &c, sizeof(c), &written, NULL) == FALSE) {
+      PlIOError (SYSTEM_ERROR,TermNil, "write to pipe returned error");
+      return(EOF);
+    }
+  }
+#else
   write(s->u.pipe.fd,  &c, sizeof(c));
+#endif
   console_count_output_char(ch,s,sno);
   return ((int) ch);
 }
@@ -1082,9 +1106,18 @@ PipeGetc(int sno)
   register StreamDesc *s = &Stream[sno];
   register int ch;
   char c;
-  int count;
 	/* should be able to use a buffer */
+#if _MSC_VER || defined(__MINGW32__) 
+  DWORD count;
+  if (WriteFile(s->u.pipe.hdl, &c, sizeof(c), &count, NULL) == FALSE) {
+    PlIOError (SYSTEM_ERROR,TermNil, "read from pipe returned error");
+    return(EOF);
+  }
+#else
+  int count;
   count = read(s->u.pipe.fd, &c, sizeof(char));
+#endif
+  printf("reading from pipe %c\n", c);
   if (count == 0) {
     ch = EOF;
   } else if (count > 0) {
@@ -1106,7 +1139,11 @@ ConsolePipeGetc(int sno)
   register StreamDesc *s = &Stream[sno];
   register int ch;
   char c;
+#if _MSC_VER || defined(__MINGW32__) 
+  DWORD count;
+#else
   int count;
+#endif
 
   /* send the prompt away */
   if (newline) {
@@ -1118,8 +1155,15 @@ ConsolePipeGetc(int sno)
     strncpy(Prompt, RepAtom (*AtPrompt)->StrOfAE, MAX_PROMPT);
     newline = FALSE;
   }
+#if _MSC_VER || defined(__MINGW32__) 
+  if (WriteFile(s->u.pipe.hdl, &c, sizeof(c), &count, NULL) == FALSE) {
+    PlIOError (SYSTEM_ERROR,TermNil, "read from pipe returned error");
+    return(EOF);
+  }
+#else
   /* should be able to use a buffer */
   count = read(s->u.pipe.fd, &c, sizeof(char));
+#endif
   if (count == 0) {
     ch = EOF;
   } else if (count > 0) {
@@ -1323,7 +1367,11 @@ GetStreamFd(int sno)
   } else
 #endif
   if (Stream[sno].status & Pipe_Stream_f) {
+#if _MSC_VER || defined(__MINGW32__) 
+    return((int)(Stream[sno].u.pipe.hdl));
+#else
     return(Stream[sno].u.pipe.fd);
+#endif
   } else if (Stream[sno].status & InMemory_Stream_f) {
     return(-1);
   }
@@ -1762,16 +1810,25 @@ p_open_pipe_stream (void)
   Term t1, t2;
   StreamDesc *st;
   int sno;
-  int filedes[2];
-
 #if  _MSC_VER || defined(__MINGW32__) 
-  if (_pipe(filedes, 256, O_TEXT) == -1)
+  HANDLE ReadPipe, WritePipe;
-#else
+  SECURITY_ATTRIBUTES satt;
-  if (pipe(filedes) != 0)
+
-#endif
+  satt.nLength = sizeof(satt);
+  satt.lpSecurityDescriptor = NULL;
+  satt.bInheritHandle = TRUE;
+  if (!CreatePipe(&ReadPipe, &WritePipe, &satt, 0))
     {
       return (PlIOError (SYSTEM_ERROR,TermNil, "open_pipe_stream/2 could not create pipe"));
     }
+#else
+  int filedes[2];
+
+  if (pipe(filedes) != 0)
+    {
+      return (PlIOError (SYSTEM_ERROR,TermNil, "open_pipe_stream/2 could not create pipe"));
+    }
+#endif
   for (sno = 0; sno < MaxStreams; ++sno)
     if (Stream[sno].status & Free_Stream_f)
       break;
@@ -1784,8 +1841,15 @@ p_open_pipe_stream (void)
   st->linecount = 1;
   st->stream_putc = PipePutc;
   st->stream_getc = PipeGetc;
-  st->stream_getc_for_read = PipeGetc;
+  if (CharConversionTable != NULL)
+    st->stream_getc_for_read = ISOGetc;
+  else
+    st->stream_getc_for_read = PipeGetc;
+#if  _MSC_VER || defined(__MINGW32__) 
+  st->u.pipe.hdl = ReadPipe;
+#else
   st->u.pipe.fd = filedes[0];
+#endif
   t1 = MkStream (sno);
   for (; sno < MaxStreams; ++sno)
     if (Stream[sno].status & Free_Stream_f)
@@ -1803,7 +1867,11 @@ p_open_pipe_stream (void)
     st->stream_getc_for_read = ISOGetc;
   else
     st->stream_getc_for_read = st->stream_getc; 
+#if  _MSC_VER || defined(__MINGW32__) 
+  st->u.pipe.hdl = WritePipe;
+#else
   st->u.pipe.fd = filedes[1];
+#endif
   t2 = MkStream (sno);
   return (unify (ARG1, t1) && unify (ARG2, t2));
 }
@@ -2234,8 +2302,13 @@ CloseStreams (int loud)
       continue;
     if ((Stream[sno].status & Popen_Stream_f))
       pclose (Stream[sno].u.file.file);
-    if ((Stream[sno].status & (Pipe_Stream_f|Socket_Stream_f)))
+#if _MSC_VER || defined(__MINGW32__) 
+    if (Stream[sno].status & Pipe_Stream_f)
+      CloseHandle (Stream[sno].u.pipe.hdl);
+#else
+    if (Stream[sno].status & (Pipe_Stream_f|Socket_Stream_f))
       close (Stream[sno].u.pipe.fd);
+#endif
 #if USE_SOCKET
     else if (Stream[sno].status & (Socket_Stream_f)) {
       CloseSocket(Stream[sno].u.socket.fd,
@@ -2274,8 +2347,12 @@ CloseStream(int sno)
 		Stream[sno].u.socket.domain);
   }
 #endif
-  else if (Stream[sno].status & (Pipe_Stream_f)) {
+  else if (Stream[sno].status & Pipe_Stream_f) {
+#if _MSC_VER || defined(__MINGW32__) 
+    CloseHandle (Stream[sno].u.pipe.hdl);
+#else
     close(Stream[sno].u.pipe.fd);
+#endif
   }
   else if (Stream[sno].status & (InMemory_Stream_f)) {
     FreeAtomSpace(Stream[sno].u.mem_string.buf);
@@ -4612,7 +4689,11 @@ StreamToFileNo(Term t)
   int sno  =
     CheckStream(t, (Input_Stream_f|Output_Stream_f), "StreamToFileNo");
   if (Stream[sno].status & Pipe_Stream_f) {
+#if _MSC_VER || defined(__MINGW32__) 
+    return((int)(Stream[sno].u.pipe.hdl));
+#else
     return(Stream[sno].u.pipe.fd);
+#endif
   } else if (Stream[sno].status & Socket_Stream_f) {
     return(Stream[sno].u.socket.fd);
   } else if (Stream[sno].status & (Null_Stream_f|InMemory_Stream_f)) {

TO_DO

@@ -1,16 +1,14 @@
 BEFORE 4.4:
-- mixed constraints and delays.
+- mixed attributes and delays.
 - write infinite terms
 - constraints in DB.
 - fix SBA plus co-routining
 - non-void temporaries going to global
-- interrupt handling in WIN32
 - timestamps on files.
 - warnings in documentation file.
 - system library
 - fix restore when code is moved around.
 - library(system) for WIN32
-- document system(library)
 - document new interface functions.
 - ^C can break code.
 - add more precision when outputting floats.
@@ -26,6 +24,11 @@ TABLING
 - make gc work after mutable var changes.
 - knap-sack
 
+PARALLELISM
+- copying: Fix stack copying after new stack.
+- SBA: fix constraint and unification.
+- IAP.
+
 AFTER 4.4(?)
 - change compilation order for arguments
 - fix code for arithmetic
@@ -35,6 +38,8 @@ AFTER 4.4(?)
 - garbage collector cleans up clauses and logical update DB.
 - atom garbage collector.
 - lpdoc.
+- incremental garbage collector.
+- threads.
 
 DONE:
 - compilation of bignums.
@@ -78,3 +83,5 @@ DONE:
 - deterministic trail entries for multi-assignment variables.
 - weird going ons with prompt and readline
 - check library(random)
+- document system(library)
+- interrupt handling in WIN32

changes4.3.html

@@ -16,6 +16,9 @@
 
 <h2>Yap-4.3.19:</h2>
 <ul>
+	<li>FIXED: get_list + unify_local was being compiled into
+	glval, breaking ENV vars </li>
+	<li>FIXED: abort was crashing in Alpha machines.</li>
 	<li>FIXED: make ^c-a work within gc.</li>
 	<li>FIXED: handle correctly very deep nested terms while gc
 	marking.</li>

library/system.yap

@@ -39,6 +39,7 @@ v/*************************************************************************
 	shell/1,
 	shell/2,
 	sleep/1,
+	system/0,
 	system/1,
 	system/2,
 	time/1,
@@ -218,55 +219,84 @@ working_directory(OLD, NEW) :-
 %
 exec(Command, [StdIn, StdOut, StdErr], PID) :-
 	G = exec(Command, [StdIn, StdOut, StdErr], PID),
-	check_command(Command, G), 
+	check_command_with_default_shell(Command, TrueCommand, G), 
-	process_inp_stream_for_exec(StdIn, In, G),
+	process_inp_stream_for_exec(StdIn, In, G, [], L1),
-	process_out_stream_for_exec(StdOut, Out, G),
+	process_out_stream_for_exec(StdOut, Out, G, L1, L2),
-	process_err_stream_for_exec(StdErr, Err, G),
+	process_err_stream_for_exec(StdErr, Err, G, L2, L3),
-	( exec_command(Command, In, Out, Err, PID, Error) -> true ; true ),
+	( exec_command(TrueCommand, In, Out, Err, PID, Error) -> true ; true ),
-	close_temp_streams(StdIn, In, StdOut, Out, StdErr, Err),
+	close_temp_streams(L3),
 	handle_system_error(Error, off, G).
 
-process_inp_stream_for_exec(Error, _, G) :- var(Error), !,
+process_inp_stream_for_exec(Error, _, G, L, L) :- var(Error), !,
 	throw(error(instantiation_error,G)).
-process_inp_stream_for_exec(null, 0, _) :- !.
+process_inp_stream_for_exec(null, null, _, L, L) :- !.
-process_inp_stream_for_exec(std, '$stream'(0), _) :- !.
+process_inp_stream_for_exec(std, 0, _, L, L) :- !.
-process_inp_stream_for_exec(pipe(SOut), SInp, _) :- !,
+process_inp_stream_for_exec(pipe(ForWriting), ForReading, _, L, [ForReading|L]) :- !,
-	open_pipe_streams(SInp, SOut).
+	open_pipe_streams(ForReading, ForWriting).
-process_inp_stream_for_exec(Stream, Stream, _) :-
+process_inp_stream_for_exec(Stream, Stream, _, L, L) :-
 	stream_property(Stream, input).
 
 
-process_out_stream_for_exec(Error, _, G) :- var(Error), !,
+process_out_stream_for_exec(Error, _, G, L, L) :- var(Error), !,
 	throw(error(instantiation_error,G)).
-process_out_stream_for_exec(null, 0, _) :- !.
+process_out_stream_for_exec(null, null, _, L, L) :- !.
-process_out_stream_for_exec(std, '$stream'(1), _) :- !.
+process_out_stream_for_exec(std, 1, _, L, L) :- !.
-process_out_stream_for_exec(pipe(SInp), SOut, _) :- !,
+process_out_stream_for_exec(pipe(ForReading), ForWriting, _, L, [ForWriting|L]) :- !,
-	open_pipe_streams(SInp, SOut).
+	open_pipe_streams(ForReading, ForWriting).
-process_out_stream_for_exec(Stream, Stream, _) :-
+process_out_stream_for_exec(Stream, Stream, _, L, L) :-
 	stream_property(Stream, output).
 
-process_err_stream_for_exec(Error, _, G) :- var(Error), !,
+process_err_stream_for_exec(Error, _, G, L, L) :- var(Error), !,
 	throw(error(instantiation_error,G)).
-process_err_stream_for_exec(null, 0, _) :- !.
+process_err_stream_for_exec(null, null, _, L, L) :- !.
-process_err_stream_for_exec(std, '$stream'(2), _) :- !.
+process_err_stream_for_exec(std, 2, _, L, L) :- !.
-process_err_stream_for_exec(pipe(SInp), SOut, _) :- !,
+process_err_stream_for_exec(pipe(ForReading), ForWriting, _, L, [ForWriting|L]) :- !,
-	open_pipe_streams(SInp, SOut).
+	open_pipe_streams(ForReading, ForWriting).
-process_err_stream_for_exec(Stream, Stream, _) :-
+process_err_stream_for_exec(Stream, Stream, _, L, L) :-
 	stream_property(Stream, output).
 
-close_temp_streams(pipe(_), S, _, _, _, _) :- close(S), fail.
+close_temp_streams([]).
-close_temp_streams(_, _, pipe(_), S, _, _) :- close(S), fail.
+close_temp_streams([S|Ss]) :- close(S),
-close_temp_streams(_, _, _, _, pipe(_), S) :- close(S), fail.
+	close_temp_streams(Ss).
-close_temp_streams(_, _, _, _, _, _).
 
 
 popen(Command, Mode, Stream) :-
 	G = popen(Command, Mode, Stream),
-	check_command(Command, G),
+	check_command_with_default_shell(Command, TrueCommand, G),
 	check_mode(Mode, M, G),
-	popen(Command, M, Stream, Result),
+	do_popen(TrueCommand, M, Stream, Result),
 	handle_system_error(Result, off, G).
 
+do_popen(Command, M, Stream, Result) :- win, !,
+	win_popen(M, Command, Stream, Result).
+do_popen(Command, M, Stream, Result) :-
+	popen(Command, M, Stream, Result).
+
+win_popen(0, Command, ForReading, Result) :-
+	open_pipe_streams(ForReading, ForWriting),
+	exec_command(Command, 0, ForWriting, 2, _, Result),
+	close(ForWriting).
+win_popen(1, Command, ForWriting, Result) :-
+	open_pipe_streams(Stream, ForWriting),
+	exec_command(Command, ForReading, 1, 2, _, Result),
+	close(ForReading).
+	
+check_command_with_default_shell(Com, ComF, G) :-
+	check_command(Com, G),
+	os_command_postprocess(Com, ComF).
+
+%
+% make sure that Windows executes the command from $COMSPEC.
+%
+os_command_postprocess(Com, ComF) :- win, !,
+	atom_codes(Com, SC),
+	append(" /c ", SC, SC1),
+	getenv('COMSPEC', Shell0),
+	atom_codes(Shell0, Codes),
+	append(Codes, SC1, SCF),
+	atom_codes(ComF, SCF).
+os_command_postprocess(Com, Com).
+
 check_command(Com, G) :- var(Com), !,
 	throw(error(instantiation_error,G)).
 check_command(Com, _) :- atom(Com), !.
@@ -283,7 +313,7 @@ check_mode(Mode, G) :-
 shell :-
 	G = shell,
 	get_shell0(FullCommand),
-	exec_command(FullCommand, '$stream'(0),'$stream'(1), '$stream'(2), PID, Error),
+	exec_command(FullCommand, 0, 1, 2, PID, Error),
 	handle_system_error(Error, off, G),
 	wait(PID, _Status, Error),
 	handle_system_error(Error, off, G).
@@ -295,7 +325,7 @@ shell(Command) :-
 	atom_codes(Command, SC),
 	append(Shell, SC, ShellCommand),
 	atom_codes(FullCommand, ShellCommand),
-	exec_command(FullCommand, '$stream'(0),'$stream'(1), '$stream'(2), PID, Error),
+	exec_command(FullCommand, 0, 1, 2, PID, Error),
 	handle_system_error(Error, off, G),
 	wait(PID, _Status, Error),
 	handle_system_error(Error, off, G).
@@ -307,7 +337,7 @@ shell(Command, Status) :-
 	atom_codes(Command, SC),
 	append(Shell, SC, ShellCommand),
 	atom_codes(FullCommand, ShellCommand),
-	exec_command(FullCommand, '$stream'(0),'$stream'(1), '$stream'(2), PID, Error),
+	exec_command(FullCommand, 0, 1, 2, PID, Error),
 	handle_system_error(Error, off, G),
 	wait(PID, Status,Error),
 	handle_system_error(Error, off, G).
@@ -315,23 +345,36 @@ shell(Command, Status) :-
 get_shell0(Shell) :-
 	getenv('SHELL', Shell), !.
 get_shell0(Shell) :-
-	win,
+	win, !,
 	getenv('COMSPEC', Shell0).
+get_shell0('/bin/sh').
 
 get_shell(Shell) :-
 	getenv('SHELL', Shell0), !,
 	atom_codes(Shell0, Codes),
 	append(Codes," -c ", Shell).
 get_shell(Shell) :-
-	win,
+	win, !,
-	getenv('COMPSEC', Shell0),
+	getenv('COMSPEC', Shell0),
 	atom_codes(Shell0, Codes),
 	append(Codes," /c ", Shell).
+get_shell("/bin/sh -c").
 	   
+system :-
+	default_shell(Command),
+	do_system(Command, _Status, Error),
+	handle_system_error(Error, off, system).
+
+default_shell(Shell) :- win, !,
+	getenv('COMSPEC', Shell).
+default_shell('/bin/sh').
+	
+
 system(Command, Status) :-
 	G = system(Command, Status),
 	check_command(Command, G),
-	do_system(Command, Status).
+	do_system(Command, Status, Error),
+	handle_system_error(Error, off, G).
 
 sleep(Interval) :- var(Interval), !,
 	throw(error(instantiation_error,sleep(Interval))).

library/system/sys.c

@@ -361,34 +361,40 @@ p_environ(void)
 }
 
 #if defined(__MINGW32__) || _MSC_VER
-static int
+static HANDLE
-get_handle(Term ti, int fd, Term tzero)
+get_handle(Term ti, DWORD fd)
 {
-  if (ti == tzero) {
+  if (IsAtomTerm(ti)) {
-    int new_fd = _dup(fd);
+    HANDLE out;
-    _close(fd);
+    SECURITY_ATTRIBUTES satt;
-    return(new_fd);
+    
+    satt.nLength = sizeof(satt);
+    satt.lpSecurityDescriptor = NULL;
+    satt.bInheritHandle = TRUE;
+    out = CreateFile("NUL",
+			    GENERIC_READ|GENERIC_WRITE,
+			    FILE_SHARE_READ|FILE_SHARE_WRITE,
+			    &satt,
+			    OPEN_EXISTING,
+			    0,
+			    NULL);
+    return(out);
   } else {
-    int sd = YapStreamToFileNo(ti), new_fd;
+    if (IsIntTerm(ti)) {
-    if (sd == fd)
+      return(GetStdHandle(fd));
-      return(-1);
+    } else
-    new_fd = _dup(fd);
+      return((HANDLE)YapStreamToFileNo(ti));
-    _close(fd);
-    _dup2(sd, fd);
-    return(new_fd);
   }
 }
 
 static void
-restore_descriptor(int fd0, int fd, Term t, Term tzero)
+close_handle(Term ti, HANDLE h)
 {
-  if (fd != -1) {
+  if (IsAtomTerm(ti)) {
-    if (t != tzero) {
+    CloseHandle(h);
-      _close(fd0);
-    }
-    _dup2(fd, fd0);
   }
 }
+
 #endif
 
 /* execute a command as a detached process */
@@ -396,18 +402,29 @@ static int
 execute_command(void)
 {
   Term ti = ARG2, to = ARG3, te = ARG4;
-  Term tzero = MkIntTerm(0);
   int res;
-  int inpf, outf, errf;
 #if defined(__MINGW32__) || _MSC_VER
+  HANDLE inpf, outf, errf;
   DWORD CreationFlags = 0;
   STARTUPINFO StartupInfo;
   PROCESS_INFORMATION ProcessInformation;
-  inpf = get_handle(ti, 0, tzero);
+  inpf = get_handle(ti, STD_INPUT_HANDLE);
-  outf = get_handle(to, 1, tzero);
+  if (inpf == INVALID_HANDLE_VALUE) {
-  errf = get_handle(te, 2, tzero);
+    return(unify(ARG6, WinError()));
-  if (inpf == -1 && outf == -1 && errf == -1) {
+  }
-    /* we do not keep a curent stream */
+  outf = get_handle(to, STD_OUTPUT_HANDLE);
+  if (outf == INVALID_HANDLE_VALUE) {
+    close_handle(ti, inpf);
+    return(unify(ARG6, WinError()));
+  }
+  errf = get_handle(te, STD_OUTPUT_HANDLE);
+  if (errf == INVALID_HANDLE_VALUE) {
+    close_handle(ti, inpf);
+    close_handle(to, outf);
+    return(unify(ARG6, WinError()));
+  }
+  if (!IsIntTerm(ti) && !IsIntTerm(to) && !IsIntTerm(te)) {
+    /* we do not keep a current stream */
     CreationFlags = DETACHED_PROCESS;
   }
   StartupInfo.cb = sizeof(STARTUPINFO);
@@ -417,9 +434,9 @@ execute_command(void)
   StartupInfo.dwFlags = STARTF_USESTDHANDLES;
   StartupInfo.cbReserved2 = 0;
   StartupInfo.lpReserved2 = NULL;
-  StartupInfo.hStdInput = GetStdHandle(STD_INPUT_HANDLE);
+  StartupInfo.hStdInput = inpf;
-  StartupInfo.hStdOutput = GetStdHandle(STD_OUTPUT_HANDLE);
+  StartupInfo.hStdOutput = outf;
-  StartupInfo.hStdError = GetStdHandle(STD_ERROR_HANDLE);
+  StartupInfo.hStdError = errf;
   /* got stdin, stdout and error as I like it */
   if (CreateProcess(NULL,
 		    AtomName(AtomOfTerm(ARG1)),
@@ -431,19 +448,27 @@ execute_command(void)
 		    NULL,
 		    &StartupInfo,
 		    &ProcessInformation) == FALSE) {
+    close_handle(ti, inpf);
+    close_handle(to, outf);
+    close_handle(te, errf);
     return(unify(ARG6, WinError()));
   }
-  restore_descriptor(0, inpf, ti, tzero);
+  close_handle(ti, inpf);
-  restore_descriptor(1, outf, to, tzero);
+  close_handle(to, outf);
-  restore_descriptor(2, errf, te, tzero);
+  close_handle(te, errf);
   res = ProcessInformation.dwProcessId;
   return(unify(ARG5,MkIntTerm(res)));  
 #else /* UNIX CODE */
+  int inpf, outf, errf;
   /* process input first */
-  if (ti == tzero) {
+  if (IsAtomTerm(ti)) {
     inpf = open("/dev/null", O_RDONLY);
   } else {
-    int sd = YapStreamToFileNo(ti);
+    int sd;
+    if (IsIntTerm(ti))
+      sd = 0;
+    else
+      sd = YapStreamToFileNo(ti);
     inpf = dup(sd);
   }
   if (inpf < 0) {
@@ -451,25 +476,36 @@ execute_command(void)
     return(unify(ARG6, MkIntTerm(errno)));
   }
   /* then output stream */
-  if (to == tzero) {
+  if (IsAtomTerm(to)) {
     outf = open("/dev/zero", O_WRONLY);
   } else {
-    int sd = YapStreamToFileNo(to);
+    int sd;
+    if (IsIntTerm(to))
+      sd = 1;
+    else
+      sd = YapStreamToFileNo(to);
     outf = dup(sd);
   }
   if (outf < 0) {
     /* return an error number */
+    close(inpf);
     return(unify(ARG6, MkIntTerm(errno)));
   }
   /* then error stream */
-  if (te == tzero) {
+  if (IsAtomTerm(te)) {
     errf = open("/dev/zero", O_WRONLY);
   } else {
-    int sd = YapStreamToFileNo(te);
+    int sd;
+    if (IsIntTerm(te))
+      sd = 2;
+    else
+      sd = YapStreamToFileNo(te);
     errf = dup(sd);
   }
   if (errf < 0) {
     /* return an error number */
+    close(inpf);
+    close(outf);
     return(unify(ARG6, MkIntTerm(errno)));
   }
   /* we are now ready to fork */
@@ -518,6 +554,9 @@ do_system(void)
   char *command = AtomName(AtomOfTerm(ARG1));
   int sys = system(command);
 #if HAVE_SYSTEM
+  if (sys < 0) {
+    return(unify(ARG3,MkIntTerm(errno)));
+  }
   return(unify(ARG2, MkIntTerm(sys)));
 #endif
 }
@@ -730,7 +769,7 @@ init_sys(void)
   UserCPredicate("dir_separator", dir_separator, 1);
   UserCPredicate("p_environ", p_environ, 2);
   UserCPredicate("exec_command", execute_command, 6);
-  UserCPredicate("do_system", do_system, 2);
+  UserCPredicate("do_system", do_system, 3);
   UserCPredicate("popen", p_popen, 4);
   UserCPredicate("wait", p_wait, 3);
   UserCPredicate("host_name", host_name, 2);