summaryrefslogtreecommitdiffstats
path: root/generic/tclMain.c
blob: 60425d9339018203ade2625bbc101417339a96eb (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
/*
 * tclMain.c --
 *
 *	Main program for Tcl shells and other Tcl-based applications.
 *
 * Copyright (c) 1988-1994 The Regents of the University of California.
 * Copyright (c) 1994-1997 Sun Microsystems, Inc.
 * Copyright (c) 2000 Ajuba Solutions.
 *
 * See the file "license.terms" for information on usage and redistribution of
 * this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tclMain.c,v 1.48 2010/02/24 10:32:17 dkf Exp $
 */

#include "tclInt.h"

#undef TCL_STORAGE_CLASS
#define TCL_STORAGE_CLASS DLLEXPORT

/*
 * The default prompt used when the user has not overridden it.
 */

#define DEFAULT_PRIMARY_PROMPT	"% "

/*
 * Declarations for various library functions and variables (don't want to
 * include tclPort.h here, because people might copy this file out of the Tcl
 * source directory to make their own modified versions).
 */

extern CRTIMPORT int	isatty(int fd);

typedef struct StartupScript {
    Tcl_Obj *path;	/* The filename of the script for *_Main() routines
			 * to [source] as a startup script, or NULL for
			 * none set, meaning enter interactive mode. */
    Tcl_Obj *encoding;	/* The encoding of the startup script file. */
} StartupScript;

static Tcl_ThreadDataKey startupScriptKey;

static Tcl_MainLoopProc *mainLoopProc = NULL;

/*
 * Structure definition for information used to keep the state of an
 * interactive command processor that reads lines from standard input and
 * writes prompts and results to standard output.
 */

typedef enum {
    PROMPT_NONE,		/* Print no prompt */
    PROMPT_START,		/* Print prompt for command start */
    PROMPT_CONTINUE		/* Print prompt for command continuation */
} PromptType;

typedef struct InteractiveState {
    Tcl_Channel input;		/* The standard input channel from which lines
				 * are read. */
    int tty;			/* Non-zero means standard input is a
				 * terminal-like device. Zero means it's a
				 * file. */
    Tcl_Obj *commandPtr;	/* Used to assemble lines of input into Tcl
				 * commands. */
    PromptType prompt;		/* Next prompt to print */
    Tcl_Interp *interp;		/* Interpreter that evaluates interactive
				 * commands. */
} InteractiveState;

/*
 * Forward declarations for functions defined later in this file.
 */

static void		Prompt(Tcl_Interp *interp, PromptType *promptPtr);
static void		StdinProc(ClientData clientData, int mask);

/*
 *----------------------------------------------------------------------
 *
 * Tcl_SetStartupScript --
 *
 *	Sets the path and encoding of the startup script to be evaluated by
 *	Tcl_Main, used to override the command line processing.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *
 *----------------------------------------------------------------------
 */

void
Tcl_SetStartupScript(
    Tcl_Obj *path,		/* Filesystem path of startup script file */
    const char *encoding)	/* Encoding of the data in that file */
{
    StartupScript *scriptPtr = Tcl_GetThreadData(&startupScriptKey,
	    (int) sizeof(StartupScript));
    Tcl_Obj *newEncoding = NULL;

    if (encoding != NULL) {
	newEncoding = Tcl_NewStringObj(encoding, -1);
    }

    if (scriptPtr->path != NULL) {
	Tcl_DecrRefCount(scriptPtr->path);
    }
    scriptPtr->path = path;
    if (scriptPtr->path != NULL) {
	Tcl_IncrRefCount(scriptPtr->path);
    }

    if (scriptPtr->encoding != NULL) {
	Tcl_DecrRefCount(scriptPtr->encoding);
    }
    scriptPtr->encoding = newEncoding;
    if (scriptPtr->encoding != NULL) {
	Tcl_IncrRefCount(scriptPtr->encoding);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetStartupScript --
 *
 *	Gets the path and encoding of the startup script to be evaluated by
 *	Tcl_Main.
 *
 * Results:
 *	The path of the startup script; NULL if none has been set.
 *
 * Side effects:
 *	If encodingPtr is not NULL, stores a (const char *) in it pointing to
 *	the encoding name registered for the startup script. Tcl retains
 *	ownership of the string, and may free it. Caller should make a copy
 *	for long-term use.
 *
 *----------------------------------------------------------------------
 */

Tcl_Obj *
Tcl_GetStartupScript(
    const char **encodingPtr)	/* When not NULL, points to storage for the
				 * (const char *) that points to the
				 * registered encoding name for the startup
				 * script */
{
    StartupScript *scriptPtr = Tcl_GetThreadData(&startupScriptKey,
	    (int) sizeof(StartupScript));

    if (encodingPtr != NULL) {
	if (scriptPtr->encoding == NULL) {
	    *encodingPtr = NULL;
	} else {
	    *encodingPtr = Tcl_GetString(scriptPtr->encoding);
	}
    }
    return scriptPtr->path;
}

/*----------------------------------------------------------------------
 *
 * Tcl_SourceRCFile --
 *
 *	This function is typically invoked by Tcl_Main of Tk_Main function to
 *	source an application specific rc file into the interpreter at startup
 *	time.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Depends on what's in the rc script.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_SourceRCFile(
    Tcl_Interp *interp)		/* Interpreter to source rc file into. */
{
    Tcl_DString temp;
    const char *fileName;
    Tcl_Channel errChannel;

    fileName = Tcl_GetVar(interp, "tcl_rcFileName", TCL_GLOBAL_ONLY);
    if (fileName != NULL) {
	Tcl_Channel c;
	const char *fullName;

	Tcl_DStringInit(&temp);
	fullName = Tcl_TranslateFileName(interp, fileName, &temp);
	if (fullName == NULL) {
	    /*
	     * Couldn't translate the file name (e.g. it referred to a bogus
	     * user or there was no HOME environment variable). Just do
	     * nothing.
	     */
	} else {
	    /*
	     * Test for the existence of the rc file before trying to read it.
	     */

	    c = Tcl_OpenFileChannel(NULL, fullName, "r", 0);
	    if (c != NULL) {
		Tcl_Close(NULL, c);
		if (Tcl_EvalFile(interp, fullName) != TCL_OK) {
		    errChannel = Tcl_GetStdChannel(TCL_STDERR);
		    if (errChannel) {
			Tcl_WriteObj(errChannel, Tcl_GetObjResult(interp));
			Tcl_WriteChars(errChannel, "\n", 1);
		    }
		}
	    }
	}
	Tcl_DStringFree(&temp);
    }
}

/*----------------------------------------------------------------------
 *
 * Tcl_Main --
 *
 *	Main program for tclsh and most other Tcl-based applications.
 *
 * Results:
 *	None. This function never returns (it exits the process when it's
 *	done).
 *
 * Side effects:
 *	This function initializes the Tcl world and then starts interpreting
 *	commands; almost anything could happen, depending on the script being
 *	interpreted.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_Main(
    int argc,			/* Number of arguments. */
    char **argv,		/* Array of argument strings. */
    Tcl_AppInitProc *appInitProc)
				/* Application-specific initialization
				 * function to call after most initialization
				 * but before starting to execute commands. */
{
    Tcl_Obj *path, *resultPtr, *argvPtr, *commandPtr = NULL;
    const char *encodingName = NULL;
    PromptType prompt = PROMPT_START;
    int code, length, tty, exitCode = 0;
    Tcl_Channel inChannel, outChannel, errChannel;
    Tcl_Interp *interp;
    Tcl_DString appName;

    Tcl_FindExecutable(argv[0]);

    interp = Tcl_CreateInterp();
    Tcl_InitMemory(interp);

    /*
     * If the application has not already set a startup script, parse the
     * first few command line arguments to determine the script path and
     * encoding.
     */

    if (NULL == Tcl_GetStartupScript(NULL)) {
	/*
	 * Check whether first 3 args (argv[1] - argv[3]) look like
	 *	-encoding ENCODING FILENAME
	 * or like
	 *	FILENAME
	 */

	if ((argc > 3) && (0 == strcmp("-encoding", argv[1]))
		&& ('-' != argv[3][0])) {
	    Tcl_SetStartupScript(Tcl_NewStringObj(argv[3], -1), argv[2]);
	    argc -= 3;
	    argv += 3;
	} else if ((argc > 1) && ('-' != argv[1][0])) {
	    Tcl_SetStartupScript(Tcl_NewStringObj(argv[1], -1), NULL);
	    argc--;
	    argv++;
	}
    }

    path = Tcl_GetStartupScript(&encodingName);
    if (path == NULL) {
	Tcl_ExternalToUtfDString(NULL, argv[0], -1, &appName);
    } else {
	const char *pathName = Tcl_GetStringFromObj(path, &length);

	Tcl_ExternalToUtfDString(NULL, pathName, length, &appName);
	path = Tcl_NewStringObj(Tcl_DStringValue(&appName), -1);
	Tcl_SetStartupScript(path, encodingName);
    }
    Tcl_SetVar(interp, "argv0", Tcl_DStringValue(&appName), TCL_GLOBAL_ONLY);
    Tcl_DStringFree(&appName);
    argc--;
    argv++;

    Tcl_SetVar2Ex(interp, "argc", NULL, Tcl_NewIntObj(argc), TCL_GLOBAL_ONLY);

    argvPtr = Tcl_NewListObj(0, NULL);
    while (argc--) {
	Tcl_DString ds;

	Tcl_ExternalToUtfDString(NULL, *argv++, -1, &ds);
	Tcl_ListObjAppendElement(NULL, argvPtr, Tcl_NewStringObj(
		Tcl_DStringValue(&ds), Tcl_DStringLength(&ds)));
	Tcl_DStringFree(&ds);
    }
    Tcl_SetVar2Ex(interp, "argv", NULL, argvPtr, TCL_GLOBAL_ONLY);

    /*
     * Set the "tcl_interactive" variable.
     */

    tty = isatty(0);
    Tcl_SetVar(interp, "tcl_interactive", ((path == NULL) && tty) ? "1" : "0",
	    TCL_GLOBAL_ONLY);

    /*
     * Invoke application-specific initialization.
     */

    Tcl_Preserve(interp);
    if (appInitProc(interp) != TCL_OK) {
	errChannel = Tcl_GetStdChannel(TCL_STDERR);
	if (errChannel) {
	    Tcl_WriteChars(errChannel,
		    "application-specific initialization failed: ", -1);
	    Tcl_WriteObj(errChannel, Tcl_GetObjResult(interp));
	    Tcl_WriteChars(errChannel, "\n", 1);
	}
    }
    if (Tcl_InterpDeleted(interp)) {
	goto done;
    }
    if (Tcl_LimitExceeded(interp)) {
	goto done;
    }

    /*
     * If a script file was specified then just source that file and quit.
     * Must fetch it again, as the appInitProc might have reset it.
     */

    path = Tcl_GetStartupScript(&encodingName);
    if (path != NULL) {
	code = Tcl_FSEvalFileEx(interp, path, encodingName);
	if (code != TCL_OK) {
	    errChannel = Tcl_GetStdChannel(TCL_STDERR);
	    if (errChannel) {
		Tcl_Obj *options = Tcl_GetReturnOptions(interp, code);
		Tcl_Obj *keyPtr, *valuePtr;

		TclNewLiteralStringObj(keyPtr, "-errorinfo");
		Tcl_IncrRefCount(keyPtr);
		Tcl_DictObjGet(NULL, options, keyPtr, &valuePtr);
		Tcl_DecrRefCount(keyPtr);

		if (valuePtr) {
		    Tcl_WriteObj(errChannel, valuePtr);
		}
		Tcl_WriteChars(errChannel, "\n", 1);
	    }
	    exitCode = 1;
	}
	goto done;
    }

    /*
     * We're running interactively. Source a user-specific startup file if the
     * application specified one and if the file exists.
     */

    Tcl_SourceRCFile(interp);
    if (Tcl_LimitExceeded(interp)) {
	goto done;
    }

    /*
     * Process commands from stdin until there's an end-of-file. Note that we
     * need to fetch the standard channels again after every eval, since they
     * may have been changed.
     */

    commandPtr = Tcl_NewObj();
    Tcl_IncrRefCount(commandPtr);

    /*
     * Get a new value for tty if anyone writes to ::tcl_interactive
     */

    Tcl_LinkVar(interp, "tcl_interactive", (char *) &tty, TCL_LINK_BOOLEAN);
    inChannel = Tcl_GetStdChannel(TCL_STDIN);
    outChannel = Tcl_GetStdChannel(TCL_STDOUT);
    while ((inChannel != NULL) && !Tcl_InterpDeleted(interp)) {
	if (mainLoopProc == NULL) {
	    if (tty) {
		Prompt(interp, &prompt);
		if (Tcl_InterpDeleted(interp)) {
		    break;
		}
		if (Tcl_LimitExceeded(interp)) {
		    break;
		}
		inChannel = Tcl_GetStdChannel(TCL_STDIN);
		if (inChannel == NULL) {
		    break;
		}
	    }
	    if (Tcl_IsShared(commandPtr)) {
		Tcl_DecrRefCount(commandPtr);
		commandPtr = Tcl_DuplicateObj(commandPtr);
		Tcl_IncrRefCount(commandPtr);
	    }
	    length = Tcl_GetsObj(inChannel, commandPtr);
	    if (length < 0) {
		if (Tcl_InputBlocked(inChannel)) {
		    /*
		     * This can only happen if stdin has been set to
		     * non-blocking. In that case cycle back and try again.
		     * This sets up a tight polling loop (since we have no
		     * event loop running). If this causes bad CPU hogging, we
		     * might try toggling the blocking on stdin instead.
		     */

		    continue;
		}

		/*
		 * Either EOF, or an error on stdin; we're done
		 */

		break;
	    }

	    /*
	     * Add the newline removed by Tcl_GetsObj back to the string. Have
	     * to add it back before testing completeness, because it can make
	     * a difference. [Bug 1775878]
	     */

	    if (Tcl_IsShared(commandPtr)) {
		Tcl_DecrRefCount(commandPtr);
		commandPtr = Tcl_DuplicateObj(commandPtr);
		Tcl_IncrRefCount(commandPtr);
	    }
	    Tcl_AppendToObj(commandPtr, "\n", 1);
	    if (!TclObjCommandComplete(commandPtr)) {
		prompt = PROMPT_CONTINUE;
		continue;
	    }

	    prompt = PROMPT_START;

	    /*
	     * The final newline is syntactically redundant, and causes some
	     * error messages troubles deeper in, so lop it back off.
	     */

	    Tcl_GetStringFromObj(commandPtr, &length);
	    Tcl_SetObjLength(commandPtr, --length);
	    code = Tcl_RecordAndEvalObj(interp, commandPtr, TCL_EVAL_GLOBAL);
	    inChannel = Tcl_GetStdChannel(TCL_STDIN);
	    outChannel = Tcl_GetStdChannel(TCL_STDOUT);
	    errChannel = Tcl_GetStdChannel(TCL_STDERR);
	    Tcl_DecrRefCount(commandPtr);
	    commandPtr = Tcl_NewObj();
	    Tcl_IncrRefCount(commandPtr);
	    if (code != TCL_OK) {
		if (errChannel) {
		    Tcl_WriteObj(errChannel, Tcl_GetObjResult(interp));
		    Tcl_WriteChars(errChannel, "\n", 1);
		}
	    } else if (tty) {
		resultPtr = Tcl_GetObjResult(interp);
		Tcl_IncrRefCount(resultPtr);
		Tcl_GetStringFromObj(resultPtr, &length);
		if ((length > 0) && outChannel) {
		    Tcl_WriteObj(outChannel, resultPtr);
		    Tcl_WriteChars(outChannel, "\n", 1);
		}
		Tcl_DecrRefCount(resultPtr);
	    }
	} else {	/* (mainLoopProc != NULL) */
	    /*
	     * If a main loop has been defined while running interactively, we
	     * want to start a fileevent based prompt by establishing a
	     * channel handler for stdin.
	     */

	    InteractiveState *isPtr = NULL;

	    if (inChannel) {
		if (tty) {
		    Prompt(interp, &prompt);
		}
		isPtr = (InteractiveState *)
			ckalloc(sizeof(InteractiveState));
		isPtr->input = inChannel;
		isPtr->tty = tty;
		isPtr->commandPtr = commandPtr;
		isPtr->prompt = prompt;
		isPtr->interp = interp;

		Tcl_UnlinkVar(interp, "tcl_interactive");
		Tcl_LinkVar(interp, "tcl_interactive", (char *) &(isPtr->tty),
			TCL_LINK_BOOLEAN);

		Tcl_CreateChannelHandler(inChannel, TCL_READABLE, StdinProc,
			isPtr);
	    }

	    mainLoopProc();
	    mainLoopProc = NULL;

	    if (inChannel) {
		tty = isPtr->tty;
		Tcl_UnlinkVar(interp, "tcl_interactive");
		Tcl_LinkVar(interp, "tcl_interactive", (char *) &tty,
			TCL_LINK_BOOLEAN);
		prompt = isPtr->prompt;
		commandPtr = isPtr->commandPtr;
		if (isPtr->input != NULL) {
		    Tcl_DeleteChannelHandler(isPtr->input, StdinProc, isPtr);
		}
		ckfree((char *) isPtr);
	    }
	    inChannel = Tcl_GetStdChannel(TCL_STDIN);
	    outChannel = Tcl_GetStdChannel(TCL_STDOUT);
	    errChannel = Tcl_GetStdChannel(TCL_STDERR);
	}
#ifdef TCL_MEM_DEBUG

	/*
	 * This code here only for the (unsupported and deprecated) [checkmem]
	 * command.
	 */

	if (tclMemDumpFileName != NULL) {
	    mainLoopProc = NULL;
	    Tcl_DeleteInterp(interp);
	}
#endif
    }

  done:
    if ((exitCode == 0) && (mainLoopProc != NULL)
	    && !Tcl_LimitExceeded(interp)) {
	/*
	 * If everything has gone OK so far, call the main loop proc, if it
	 * exists. Packages (like Tk) can set it to start processing events at
	 * this point.
	 */

	mainLoopProc();
	mainLoopProc = NULL;
    }
    if (commandPtr != NULL) {
	Tcl_DecrRefCount(commandPtr);
    }

    /*
     * Rather than calling exit, invoke the "exit" command so that users can
     * replace "exit" with some other command to do additional cleanup on
     * exit. The Tcl_EvalObjEx call should never return.
     */

    if (!Tcl_InterpDeleted(interp)) {
	if (!Tcl_LimitExceeded(interp)) {
	    Tcl_Obj *cmd = Tcl_ObjPrintf("exit %d", exitCode);

	    Tcl_IncrRefCount(cmd);
	    Tcl_EvalObjEx(interp, cmd, TCL_EVAL_GLOBAL);
	    Tcl_DecrRefCount(cmd);
	}

	/*
	 * If Tcl_EvalObjEx returns, trying to eval [exit], something unusual
	 * is happening. Maybe interp has been deleted; maybe [exit] was
	 * redefined, maybe we've blown up because of an exceeded limit. We
	 * still want to cleanup and exit.
	 */

	if (!Tcl_InterpDeleted(interp)) {
	    Tcl_DeleteInterp(interp);
	}
    }
    Tcl_SetStartupScript(NULL, NULL);

    /*
     * If we get here, the master interp has been deleted. Allow its
     * destruction with the last matching Tcl_Release.
     */

    Tcl_Release(interp);
    Tcl_Exit(exitCode);
}

/*
 *---------------------------------------------------------------
 *
 * Tcl_SetMainLoop --
 *
 *	Sets an alternative main loop function.
 *
 * Results:
 *	Returns the previously defined main loop function.
 *
 * Side effects:
 *	This function will be called before Tcl exits, allowing for the
 *	creation of an event loop.
 *
 *---------------------------------------------------------------
 */

void
Tcl_SetMainLoop(
    Tcl_MainLoopProc *proc)
{
    mainLoopProc = proc;
}

/*
 *----------------------------------------------------------------------
 *
 * StdinProc --
 *
 *	This function is invoked by the event dispatcher whenever standard
 *	input becomes readable. It grabs the next line of input characters,
 *	adds them to a command being assembled, and executes the command if
 *	it's complete.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Could be almost arbitrary, depending on the command that's typed.
 *
 *----------------------------------------------------------------------
 */

    /* ARGSUSED */
static void
StdinProc(
    ClientData clientData,	/* The state of interactive cmd line */
    int mask)			/* Not used. */
{
    InteractiveState *isPtr = clientData;
    Tcl_Channel chan = isPtr->input;
    Tcl_Obj *commandPtr = isPtr->commandPtr;
    Tcl_Interp *interp = isPtr->interp;
    int code, length;

    if (Tcl_IsShared(commandPtr)) {
	Tcl_DecrRefCount(commandPtr);
	commandPtr = Tcl_DuplicateObj(commandPtr);
	Tcl_IncrRefCount(commandPtr);
    }
    length = Tcl_GetsObj(chan, commandPtr);
    if (length < 0) {
	if (Tcl_InputBlocked(chan)) {
	    return;
	}
	if (isPtr->tty) {
	    /*
	     * Would be better to find a way to exit the mainLoop? Or perhaps
	     * evaluate [exit]? Leaving as is for now due to compatibility
	     * concerns.
	     */

	    Tcl_Exit(0);
	}
	Tcl_DeleteChannelHandler(chan, StdinProc, isPtr);
	return;
    }

    if (Tcl_IsShared(commandPtr)) {
	Tcl_DecrRefCount(commandPtr);
	commandPtr = Tcl_DuplicateObj(commandPtr);
	Tcl_IncrRefCount(commandPtr);
    }
    Tcl_AppendToObj(commandPtr, "\n", 1);
    if (!TclObjCommandComplete(commandPtr)) {
	isPtr->prompt = PROMPT_CONTINUE;
	goto prompt;
    }
    isPtr->prompt = PROMPT_START;
    Tcl_GetStringFromObj(commandPtr, &length);
    Tcl_SetObjLength(commandPtr, --length);

    /*
     * Disable the stdin channel handler while evaluating the command;
     * otherwise if the command re-enters the event loop we might process
     * commands from stdin before the current command is finished. Among other
     * things, this will trash the text of the command being evaluated.
     */

    Tcl_CreateChannelHandler(chan, 0, StdinProc, isPtr);
    code = Tcl_RecordAndEvalObj(interp, commandPtr, TCL_EVAL_GLOBAL);
    isPtr->input = chan = Tcl_GetStdChannel(TCL_STDIN);
    Tcl_DecrRefCount(commandPtr);
    isPtr->commandPtr = commandPtr = Tcl_NewObj();
    Tcl_IncrRefCount(commandPtr);
    if (chan != NULL) {
	Tcl_CreateChannelHandler(chan, TCL_READABLE, StdinProc, isPtr);
    }
    if (code != TCL_OK) {
	Tcl_Channel errChannel = Tcl_GetStdChannel(TCL_STDERR);

	if (errChannel != NULL) {
	    Tcl_WriteObj(errChannel, Tcl_GetObjResult(interp));
	    Tcl_WriteChars(errChannel, "\n", 1);
	}
    } else if (isPtr->tty) {
	Tcl_Obj *resultPtr = Tcl_GetObjResult(interp);
	Tcl_Channel outChannel = Tcl_GetStdChannel(TCL_STDOUT);

	Tcl_IncrRefCount(resultPtr);
	Tcl_GetStringFromObj(resultPtr, &length);
	if ((length >0) && (outChannel != NULL)) {
	    Tcl_WriteObj(outChannel, resultPtr);
	    Tcl_WriteChars(outChannel, "\n", 1);
	}
	Tcl_DecrRefCount(resultPtr);
    }

    /*
     * If a tty stdin is still around, output a prompt.
     */

  prompt:
    if (isPtr->tty && (isPtr->input != NULL)) {
	Prompt(interp, &isPtr->prompt);
	isPtr->input = Tcl_GetStdChannel(TCL_STDIN);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Prompt --
 *
 *	Issue a prompt on standard output, or invoke a script to issue the
 *	prompt.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	A prompt gets output, and a Tcl script may be evaluated in interp.
 *
 *----------------------------------------------------------------------
 */

static void
Prompt(
    Tcl_Interp *interp,		/* Interpreter to use for prompting. */
    PromptType *promptPtr)	/* Points to type of prompt to print. Filled
				 * with PROMPT_NONE after a prompt is
				 * printed. */
{
    Tcl_Obj *promptCmdPtr;
    int code;
    Tcl_Channel outChannel, errChannel;

    if (*promptPtr == PROMPT_NONE) {
	return;
    }

    promptCmdPtr = Tcl_GetVar2Ex(interp,
	    ((*promptPtr == PROMPT_CONTINUE) ? "tcl_prompt2" : "tcl_prompt1"),
	    NULL, TCL_GLOBAL_ONLY);

    if (Tcl_InterpDeleted(interp)) {
	return;
    }
    if (promptCmdPtr == NULL) {
    defaultPrompt:
	outChannel = Tcl_GetStdChannel(TCL_STDOUT);
	if ((*promptPtr == PROMPT_START) && (outChannel != NULL)) {
	    Tcl_WriteChars(outChannel, DEFAULT_PRIMARY_PROMPT,
		    strlen(DEFAULT_PRIMARY_PROMPT));
	}
    } else {
	code = Tcl_EvalObjEx(interp, promptCmdPtr, TCL_EVAL_GLOBAL);
	if (code != TCL_OK) {
	    Tcl_AddErrorInfo(interp,
		    "\n    (script that generates prompt)");
	    errChannel = Tcl_GetStdChannel(TCL_STDERR);
	    if (errChannel != NULL) {
		Tcl_WriteObj(errChannel, Tcl_GetObjResult(interp));
		Tcl_WriteChars(errChannel, "\n", 1);
	    }
	    goto defaultPrompt;
	}
    }

    outChannel = Tcl_GetStdChannel(TCL_STDOUT);
    if (outChannel != NULL) {
	Tcl_Flush(outChannel);
    }
    *promptPtr = PROMPT_NONE;
}

/*
 * Local Variables:
 * mode: c
 * c-basic-offset: 4
 * fill-column: 78
 * End:
 */