2 '\" Copyright (c) 1996-1997 Sun Microsystems, Inc.
4 '\" See the file "license.terms" for information on usage and redistribution
5 '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
7 '\" RCS: @(#) $Id: OpenFileChnl.3,v 1.20.2.2 2003/10/07 15:25:46 dgp Exp $
8 '\" The definitions below are for supplemental macros used in Tcl/Tk
11 '\" .AP type name in/out ?indent?
12 '\" Start paragraph describing an argument to a library procedure.
13 '\" type is type of argument (int, etc.), in/out is either "in", "out",
14 '\" or "in/out" to describe whether procedure reads or modifies arg,
15 '\" and indent is equivalent to second arg of .IP (shouldn't ever be
16 '\" needed; use .AS below instead)
19 '\" Give maximum sizes of arguments for setting tab stops. Type and
20 '\" name are examples of largest possible arguments that will be passed
21 '\" to .AP later. If args are omitted, default tab stops are used.
24 '\" Start box enclosure. From here until next .BE, everything will be
25 '\" enclosed in one large box.
28 '\" End of box enclosure.
31 '\" Begin code excerpt.
36 '\" .VS ?version? ?br?
37 '\" Begin vertical sidebar, for use in marking newly-changed parts
38 '\" of man pages. The first argument is ignored and used for recording
39 '\" the version when the .VS was added, so that the sidebars can be
40 '\" found and removed when they reach a certain age. If another argument
41 '\" is present, then a line break is forced before starting the sidebar.
44 '\" End of vertical sidebar.
47 '\" Begin an indented unfilled display.
50 '\" End of indented unfilled display.
53 '\" Start of list of standard options for a Tk widget. The
54 '\" options follow on successive lines, in four columns separated
58 '\" End of list of standard options for a Tk widget.
60 '\" .OP cmdName dbName dbClass
61 '\" Start of description of a specific option. cmdName gives the
62 '\" option's name as specified in the class command, dbName gives
63 '\" the option's name in the option database, and dbClass gives
64 '\" the option's class in the option database.
67 '\" Print arg1 underlined, then print arg2 normally.
69 '\" RCS: @(#) $Id: man.macros,v 1.4 2000/08/25 06:18:32 ericm Exp $
71 '\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages.
75 '\" # Start an argument description
79 . ie !"\\$2"" .TP \\n()Cu
84 \&\\$1 \\fI\\$2\\fP (\\$3)
97 '\" # define tabbing values for .AP
100 .if !"\\$1"" .nr )A \\w'\\$1'u+3n
103 .if !"\\$2"" .nr )B \\w'\\$2'u+\\n()Au+3n
104 .nr )C \\n()Bu+\\w'(in/out)'u+2n
106 .AS Tcl_Interp Tcl_CreateInterp in/out
107 '\" # BS - start boxed text
108 '\" # ^y = starting y location
116 .if n \l'\\n(.lu\(ul'
119 '\" # BE - end boxed text (draw box now)
124 .ie n \l'\\n(^lu\(ul'
126 .\" Draw four-sided box normally, but don't draw top of
127 .\" box if the box started on an earlier page.
129 \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul'
132 \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul'
139 '\" # VS - start vertical sidebar
140 '\" # ^Y = starting y location
141 '\" # ^v = 1 (for troff; for nroff this doesn't matter)
145 .ie n 'mc \s12\(br\s0
148 '\" # VE - end of vertical sidebar
156 \h'|\\n(^lu+3n'\L'|\\n(^Yu-1v\(bv'\v'\\n(^tu+1v-\\n(^Yu'\h'-|\\n(^lu+3n'
163 '\" # Special macro to handle page bottom: finish off current
164 '\" # box/sidebar if in box/sidebar mode, then invoked standard
165 '\" # page bottom macro.
172 .\" Draw three-sided box if this is the box's first page,
173 .\" draw two sides but no top otherwise.
174 .ie !\\n(^b-1 \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c
175 .el \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c
178 .nr ^x \\n(^tu+1v-\\n(^Yu
179 \kx\h'-\\nxu'\h'|\\n(^lu+3n'\ky\L'-\\n(^xu'\v'\\n(^xu'\h'|0u'\c
192 '\" # DS - begin display
198 '\" # DE - end display
204 '\" # SO - start of list of standard options
206 .SH "STANDARD OPTIONS"
212 '\" # SE - end of list of standard options
217 See the \\fBoptions\\fR manual entry for details on the standard options.
219 '\" # OP - start of full description for a single option
224 Command-Line Name: \\fB\\$1\\fR
225 Database Name: \\fB\\$2\\fR
226 Database Class: \\fB\\$3\\fR
230 '\" # CS - begin code excerpt
236 '\" # CE - end code excerpt
244 .TH Tcl_OpenFileChannel 3 8.3 Tcl "Tcl Library Procedures"
246 '\" Note: do not modify the .SH NAME line immediately below!
248 Tcl_OpenFileChannel, Tcl_OpenCommandChannel, Tcl_MakeFileChannel, Tcl_GetChannel, Tcl_GetChannelNames, Tcl_GetChannelNamesEx, Tcl_RegisterChannel, Tcl_UnregisterChannel, Tcl_DetachChannel, Tcl_IsStandardChannel, Tcl_Close, Tcl_ReadChars, Tcl_Read, Tcl_GetsObj, Tcl_Gets, Tcl_WriteObj, Tcl_WriteChars, Tcl_Write, Tcl_Flush, Tcl_Seek, Tcl_Tell, Tcl_GetChannelOption, Tcl_SetChannelOption, Tcl_Eof, Tcl_InputBlocked, Tcl_InputBuffered, Tcl_OutputBuffered, Tcl_Ungets, Tcl_ReadRaw, Tcl_WriteRaw \- buffered I/O facilities using channels
251 \fB#include <tcl.h>\fR
254 \fBTcl_OpenFileChannel\fR(\fIinterp, fileName, mode, permissions\fR)
257 \fBTcl_OpenCommandChannel\fR(\fIinterp, argc, argv, flags\fR)
260 \fBTcl_MakeFileChannel\fR(\fIhandle, readOrWrite\fR)
263 \fBTcl_GetChannel\fR(\fIinterp, channelName, modePtr\fR)
267 \fBTcl_GetChannelNames\fR(\fIinterp\fR)
270 \fBTcl_GetChannelNamesEx\fR(\fIinterp, pattern\fR)
274 \fBTcl_RegisterChannel\fR(\fIinterp, channel\fR)
277 \fBTcl_UnregisterChannel\fR(\fIinterp, channel\fR)
280 \fBTcl_DetachChannel\fR(\fIinterp, channel\fR)
283 \fBTcl_IsStandardChannel\fR(\fIchannel\fR)
286 \fBTcl_Close\fR(\fIinterp, channel\fR)
290 \fBTcl_ReadChars\fR(\fIchannel, readObjPtr, charsToRead, appendFlag\fR)
293 \fBTcl_Read\fR(\fIchannel, readBuf, bytesToRead\fR)
296 \fBTcl_GetsObj\fR(\fIchannel, lineObjPtr\fR)
299 \fBTcl_Gets\fR(\fIchannel, lineRead\fR)
302 \fBTcl_Ungets\fR(\fIchannel, input, inputLen, addAtEnd\fR)
305 \fBTcl_WriteObj\fR(\fIchannel, writeObjPtr\fR)
308 \fBTcl_WriteChars\fR(\fIchannel, charBuf, bytesToWrite\fR)
311 \fBTcl_Write\fR(\fIchannel, byteBuf, bytesToWrite\fR)
316 \fBTcl_ReadRaw\fR(\fIchannel, readBuf, bytesToRead\fR)
319 \fBTcl_WriteRaw\fR(\fIchannel, byteBuf, bytesToWrite\fR)
323 \fBTcl_Eof\fR(\fIchannel\fR)
326 \fBTcl_Flush\fR(\fIchannel\fR)
329 \fBTcl_InputBlocked\fR(\fIchannel\fR)
332 \fBTcl_InputBuffered\fR(\fIchannel\fR)
336 \fBTcl_OutputBuffered\fR(\fIchannel\fR)
341 \fBTcl_Seek\fR(\fIchannel, offset, seekMode\fR)
344 \fBTcl_Tell\fR(\fIchannel\fR)
348 \fBTcl_GetChannelOption\fR(\fIinterp, channel, optionName, optionValue\fR)
351 \fBTcl_SetChannelOption\fR(\fIinterp, channel, optionName, newValue\fR)
354 .AS Tcl_ChannelType newClientProcPtr in
355 .AP Tcl_Interp *interp in
356 Used for error reporting and to look up a channel registered in it.
357 .AP "CONST char" *fileName in
358 The name of a local or network file.
359 .AP "CONST char" *mode in
360 Specifies how the file is to be accessed. May have any of the values
361 allowed for the \fImode\fR argument to the Tcl \fBopen\fR command.
362 .AP int permissions in
363 POSIX-style permission flags such as 0644. If a new file is created, these
364 permissions will be set on the created file.
366 The number of elements in \fIargv\fR.
367 .AP "CONST char" **argv in
368 Arguments for constructing a command pipeline. These values have the same
369 meaning as the non-switch arguments to the Tcl \fBexec\fR command.
371 Specifies the disposition of the stdio handles in pipeline: OR-ed
372 combination of \fBTCL_STDIN\fR, \fBTCL_STDOUT\fR, \fBTCL_STDERR\fR, and
373 \fBTCL_ENFORCE_MODE\fR. If \fBTCL_STDIN\fR is set, stdin for the first child
374 in the pipe is the pipe channel, otherwise it is the same as the standard
375 input of the invoking process; likewise for \fBTCL_STDOUT\fR and
376 \fBTCL_STDERR\fR. If \fBTCL_ENFORCE_MODE\fR is not set, then the pipe can
377 redirect stdio handles to override the stdio handles for which
378 \fBTCL_STDIN\fR, \fBTCL_STDOUT\fR and \fBTCL_STDERR\fR have been set. If it
379 is set, then such redirections cause an error.
380 .AP ClientData handle in
381 Operating system specific handle for I/O to a file. For Unix this is a
382 file descriptor, for Windows it is a HANDLE.
383 .AP int readOrWrite in
384 OR-ed combination of \fBTCL_READABLE\fR and \fBTCL_WRITABLE\fR to indicate
385 what operations are valid on \fIhandle\fR.
386 .AP "CONST char" *channelName in
387 The name of the channel.
389 Points at an integer variable that will receive an OR-ed combination of
390 \fBTCL_READABLE\fR and \fBTCL_WRITABLE\fR denoting whether the channel is
391 open for reading and writing.
393 .AP "CONST char" *pattern in
394 The pattern to match on, passed to Tcl_StringMatch, or NULL.
396 .AP Tcl_Channel channel in
397 A Tcl channel for input or output. Must have been the return value
398 from a procedure such as \fBTcl_OpenFileChannel\fR.
400 .AP Tcl_Obj *readObjPtr in/out
401 A pointer to a Tcl Object in which to store the characters read from the
403 .AP int charsToRead in
404 The number of characters to read from the channel. If the channel's encoding
405 is \fBbinary\fR, this is equivalent to the number of bytes to read from the
407 .AP int appendFlag in
408 If non-zero, data read from the channel will be appended to the object.
409 Otherwise, the data will replace the existing contents of the object.
410 .AP char *readBuf out
411 A buffer in which to store the bytes read from the channel.
412 .AP int bytesToRead in
413 The number of bytes to read from the channel. The buffer \fIreadBuf\fR must
414 be large enough to hold this many bytes.
415 .AP Tcl_Obj *lineObjPtr in/out
416 A pointer to a Tcl object in which to store the line read from the
417 channel. The line read will be appended to the current value of the
419 .AP Tcl_DString *lineRead in/out
420 A pointer to a Tcl dynamic string in which to store the line read from the
421 channel. Must have been initialized by the caller. The line read will be
422 appended to any data already in the dynamic string.
424 .AP "CONST char" *input in
425 The input to add to a channel buffer.
429 Flag indicating whether the input should be added to the end or
430 beginning of the channel buffer.
432 .AP Tcl_Obj *writeObjPtr in
433 A pointer to a Tcl Object whose contents will be output to the channel.
434 .AP "CONST char" *charBuf in
435 A buffer containing the characters to output to the channel.
436 .AP "CONST char" *byteBuf in
437 A buffer containing the bytes to output to the channel.
438 .AP int bytesToWrite in
439 The number of bytes to consume from \fIcharBuf\fR or \fIbyteBuf\fR and
440 output to the channel.
443 How far to move the access point in the channel at which the next input or
444 output operation will be applied, measured in bytes from the position
445 given by \fIseekMode\fR. May be either positive or negative.
447 Relative to which point to seek; used with \fIoffset\fR to calculate the new
448 access point for the channel. Legal values are \fBSEEK_SET\fR,
449 \fBSEEK_CUR\fR, and \fBSEEK_END\fR.
450 .AP "CONST char" *optionName in
451 The name of an option applicable to this channel, such as \fB\-blocking\fR.
452 May have any of the values accepted by the \fBfconfigure\fR command.
453 .AP Tcl_DString *optionValue in
454 Where to store the value of an option or a list of all options and their
455 values. Must have been initialized by the caller.
456 .AP "CONST char" *newValue in
457 New value for the option given by \fIoptionName\fR.
462 The Tcl channel mechanism provides a device-independent and
463 platform-independent mechanism for performing buffered input
464 and output operations on a variety of file, socket, and device
466 The channel mechanism is extensible to new channel types, by
467 providing a low level channel driver for the new type; the channel driver
468 interface is described in the manual entry for \fBTcl_CreateChannel\fR. The
469 channel mechanism provides a buffering scheme modeled after
470 Unix's standard I/O, and it also allows for nonblocking I/O on
473 The procedures described in this manual entry comprise the C APIs of the
474 generic layer of the channel architecture. For a description of the channel
475 driver architecture and how to implement channel drivers for new types of
476 channels, see the manual entry for \fBTcl_CreateChannel\fR.
478 .SH TCL_OPENFILECHANNEL
480 \fBTcl_OpenFileChannel\fR opens a file specified by \fIfileName\fR and
481 returns a channel handle that can be used to perform input and output on
482 the file. This API is modeled after the \fBfopen\fR procedure of
483 the Unix standard I/O library.
484 The syntax and meaning of all arguments is similar to those
485 given in the Tcl \fBopen\fR command when opening a file.
486 If an error occurs while opening the channel, \fBTcl_OpenFileChannel\fR
487 returns NULL and records a POSIX error code that can be
488 retrieved with \fBTcl_GetErrno\fR.
489 In addition, if \fIinterp\fR is non-NULL, \fBTcl_OpenFileChannel\fR
490 leaves an error message in \fIinterp\fR's result after any error.
491 As of Tcl 8.4, the object-based API \fBTcl_FSOpenFileChannel\fR should
492 be used in preference to \fBTcl_OpenFileChannel\fR wherever possible.
496 The newly created channel is not registered in the supplied interpreter; to
497 register it, use \fBTcl_RegisterChannel\fR, described below.
498 If one of the standard channels, \fBstdin, stdout\fR or \fBstderr\fR was
499 previously closed, the act of creating the new channel also assigns it as a
500 replacement for the standard channel.
502 .SH TCL_OPENCOMMANDCHANNEL
504 \fBTcl_OpenCommandChannel\fR provides a C-level interface to the
505 functions of the \fBexec\fR and \fBopen\fR commands.
506 It creates a sequence of subprocesses specified
507 by the \fIargv\fR and \fIargc\fR arguments and returns a channel that can
508 be used to communicate with these subprocesses.
509 The \fIflags\fR argument indicates what sort of communication will
510 exist with the command pipeline.
512 If the \fBTCL_STDIN\fR flag is set then the standard input for the
513 first subprocess will be tied to the channel: writing to the channel
514 will provide input to the subprocess. If \fBTCL_STDIN\fR is not set,
515 then standard input for the first subprocess will be the same as this
516 application's standard input. If \fBTCL_STDOUT\fR is set then
517 standard output from the last subprocess can be read from the channel;
518 otherwise it goes to this application's standard output. If
519 \fBTCL_STDERR\fR is set, standard error output for all subprocesses is
520 returned to the channel and results in an error when the channel is
521 closed; otherwise it goes to this application's standard error. If
522 \fBTCL_ENFORCE_MODE\fR is not set, then \fIargc\fR and \fIargv\fR can
523 redirect the stdio handles to override \fBTCL_STDIN\fR,
524 \fBTCL_STDOUT\fR, and \fBTCL_STDERR\fR; if it is set, then it is an
525 error for argc and argv to override stdio channels for which
526 \fBTCL_STDIN\fR, \fBTCL_STDOUT\fR, and \fBTCL_STDERR\fR have been set.
528 If an error occurs while opening the channel, \fBTcl_OpenCommandChannel\fR
529 returns NULL and records a POSIX error code that can be retrieved with
531 In addition, \fBTcl_OpenCommandChannel\fR leaves an error message in
532 the interpreter's result if \fIinterp\fR is not NULL.
534 The newly created channel is not registered in the supplied interpreter; to
535 register it, use \fBTcl_RegisterChannel\fR, described below.
536 If one of the standard channels, \fBstdin, stdout\fR or \fBstderr\fR was
537 previously closed, the act of creating the new channel also assigns it as a
538 replacement for the standard channel.
540 .SH TCL_MAKEFILECHANNEL
542 \fBTcl_MakeFileChannel\fR makes a \fBTcl_Channel\fR from an existing,
543 platform-specific, file handle.
544 The newly created channel is not registered in the supplied interpreter; to
545 register it, use \fBTcl_RegisterChannel\fR, described below.
546 If one of the standard channels, \fBstdin, stdout\fR or \fBstderr\fR was
547 previously closed, the act of creating the new channel also assigns it as a
548 replacement for the standard channel.
552 \fBTcl_GetChannel\fR returns a channel given the \fIchannelName\fR used to
553 create it with \fBTcl_CreateChannel\fR and a pointer to a Tcl interpreter in
554 \fIinterp\fR. If a channel by that name is not registered in that interpreter,
555 the procedure returns NULL. If the \fImodePtr\fR argument is not NULL, it
556 points at an integer variable that will receive an OR-ed combination of
557 \fBTCL_READABLE\fR and \fBTCL_WRITABLE\fR describing whether the channel is
558 open for reading and writing.
560 \fBTcl_GetChannelNames\fR and \fBTcl_GetChannelNamesEx\fR write the
561 names of the registered channels to the interpreter's result as a
562 list object. \fBTcl_GetChannelNamesEx\fR will filter these names
563 according to the \fIpattern\fR. If \fIpattern\fR is NULL, then it
564 will not do any filtering. The return value is \fBTCL_OK\fR if no
565 errors occurred writing to the result, otherwise it is \fBTCL_ERROR\fR,
566 and the error message is left in the interpreter's result.
568 .SH TCL_REGISTERCHANNEL
570 \fBTcl_RegisterChannel\fR adds a channel to the set of channels accessible
571 in \fIinterp\fR. After this call, Tcl programs executing in that
572 interpreter can refer to the channel in input or output operations using
573 the name given in the call to \fBTcl_CreateChannel\fR. After this call,
574 the channel becomes the property of the interpreter, and the caller should
575 not call \fBTcl_Close\fR for the channel; the channel will be closed
576 automatically when it is unregistered from the interpreter.
578 Code executing outside of any Tcl interpreter can call
579 \fBTcl_RegisterChannel\fR with \fIinterp\fR as NULL, to indicate that it
580 wishes to hold a reference to this channel. Subsequently, the channel can
581 be registered in a Tcl interpreter and it will only be closed when the
582 matching number of calls to \fBTcl_UnregisterChannel\fR have been made.
583 This allows code executing outside of any interpreter to safely hold a
584 reference to a channel that is also registered in a Tcl interpreter.
586 This procedure interacts with the code managing the standard
587 channels. If no standard channels were initialized before the first
588 call to \fBTcl_RegisterChannel\fR they will get initialized by that
589 call. See \fBTcl_StandardChannels\fR for a general treatise about
590 standard channels and the behaviour of the Tcl library with regard to
593 .SH TCL_UNREGISTERCHANNEL
595 \fBTcl_UnregisterChannel\fR removes a channel from the set of channels
596 accessible in \fIinterp\fR. After this call, Tcl programs will no longer be
597 able to use the channel's name to refer to the channel in that interpreter.
598 If this operation removed the last registration of the channel in any
599 interpreter, the channel is also closed and destroyed.
601 Code not associated with a Tcl interpreter can call
602 \fBTcl_UnregisterChannel\fR with \fIinterp\fR as NULL, to indicate to Tcl
603 that it no longer holds a reference to that channel. If this is the last
604 reference to the channel, it will now be closed. \fBTcl_UnregisterChannel\fR
605 is very similar to \fBTcl_DetachChannel\fR except that it will also
606 close the channel if no further references to it exist.
608 .SH TCL_DETACHCHANNEL
610 \fBTcl_DetachChannel\fR removes a channel from the set of channels
611 accessible in \fIinterp\fR. After this call, Tcl programs will no longer be
612 able to use the channel's name to refer to the channel in that interpreter.
613 Beyond that, this command has no further effect. It cannot be used on
614 the standard channels (stdout, stderr, stdin), and will return
615 TCL_ERROR if passed one of those channels.
617 Code not associated with a Tcl interpreter can call
618 \fBTcl_DetachChannel\fR with \fIinterp\fR as NULL, to indicate to Tcl
619 that it no longer holds a reference to that channel. If this is the last
620 reference to the channel, unlike \fBTcl_UnregisterChannel\fR,
621 it will not be closed.
623 .SH TCL_ISSTANDARDCHANNEL
625 \fBTcl_IsStandardChannel\fR tests whether a channel is one of the
626 three standard channels, stdin, stdout or stderr. If so, it returns
629 No attempt is made to check whether the given channel or the standard
630 channels are initialized or otherwise valid.
634 \fBTcl_Close\fR destroys the channel \fIchannel\fR, which must denote a
635 currently open channel. The channel should not be registered in any
636 interpreter when \fBTcl_Close\fR is called. Buffered output is flushed to
637 the channel's output device prior to destroying the channel, and any
638 buffered input is discarded. If this is a blocking channel, the call does
639 not return until all buffered data is successfully sent to the channel's
640 output device. If this is a nonblocking channel and there is buffered
641 output that cannot be written without blocking, the call returns
642 immediately; output is flushed in the background and the channel will be
643 closed once all of the buffered data has been output. In this case errors
644 during flushing are not reported.
646 If the channel was closed successfully, \fBTcl_Close\fR returns \fBTCL_OK\fR.
647 If an error occurs, \fBTcl_Close\fR returns \fBTCL_ERROR\fR and records a
648 POSIX error code that can be retrieved with \fBTcl_GetErrno\fR.
649 If the channel is being closed synchronously and an error occurs during
650 closing of the channel and \fIinterp\fR is not NULL, an error message is
651 left in the interpreter's result.
653 Note: it is not safe to call \fBTcl_Close\fR on a channel that has been
654 registered using \fBTcl_RegisterChannel\fR; see the documentation for
655 \fBTcl_RegisterChannel\fR, above, for details. If the channel has ever
656 been given as the \fBchan\fR argument in a call to
657 \fBTcl_RegisterChannel\fR, you should instead use
658 \fBTcl_UnregisterChannel\fR, which will internally call \fBTcl_Close\fR
659 when all calls to \fBTcl_RegisterChannel\fR have been matched by
660 corresponding calls to \fBTcl_UnregisterChannel\fR.
663 .SH "TCL_READCHARS AND TCL_READ"
665 \fBTcl_ReadChars\fR consumes bytes from \fIchannel\fR, converting the bytes
666 to UTF-8 based on the channel's encoding and storing the produced data in
667 \fIreadObjPtr\fR's string representation. The return value of
668 \fBTcl_ReadChars\fR is the number of characters, up to \fIcharsToRead\fR,
669 that were stored in \fIreadObjPtr\fR. If an error occurs while reading, the
670 return value is \-1 and \fBTcl_ReadChars\fR records a POSIX error code that
671 can be retrieved with \fBTcl_GetErrno\fR.
673 The return value may be smaller than the value to read, indicating that less
674 data than requested was available. This is called a \fIshort read\fR. In
675 blocking mode, this can only happen on an end-of-file. In nonblocking mode,
676 a short read can also occur if there is not enough input currently
677 available: \fBTcl_ReadChars\fR returns a short count rather than waiting
680 If the channel is in blocking mode, a return value of zero indicates an
681 end-of-file condition. If the channel is in nonblocking mode, a return
682 value of zero indicates either that no input is currently available or an
683 end-of-file condition. Use \fBTcl_Eof\fR and \fBTcl_InputBlocked\fR to tell
684 which of these conditions actually occurred.
686 \fBTcl_ReadChars\fR translates the various end-of-line representations into
687 the canonical \fB\en\fR internal representation according to the current
688 end-of-line recognition mode. End-of-line recognition and the various
689 platform-specific modes are described in the manual entry for the Tcl
690 \fBfconfigure\fR command.
692 As a performance optimization, when reading from a channel with the encoding
693 \fBbinary\fR, the bytes are not converted to UTF-8 as they are read.
694 Instead, they are stored in \fIreadObjPtr\fR's internal representation as a
695 byte-array object. The string representation of this object will only be
696 constructed if it is needed (e.g., because of a call to
697 \fBTcl_GetStringFromObj\fR). In this way, byte-oriented data can be read
698 from a channel, manipulated by calling \fBTcl_GetByteArrayFromObj\fR and
699 related functions, and then written to a channel without the expense of ever
700 converting to or from UTF-8.
702 \fBTcl_Read\fR is similar to \fBTcl_ReadChars\fR, except that it doesn't do
703 encoding conversions, regardless of the channel's encoding. It is deprecated
704 and exists for backwards compatibility with non-internationalized Tcl
705 extensions. It consumes bytes from \fIchannel\fR and stores them in
706 \fIreadBuf\fR, performing end-of-line translations on the way. The return value
707 of \fBTcl_Read\fR is the number of bytes, up to \fIbytesToRead\fR, written in
708 \fIreadBuf\fR. The buffer produced by \fBTcl_Read\fR is not null-terminated.
709 Its contents are valid from the zeroth position up to and excluding the
710 position indicated by the return value.
712 \fBTcl_ReadRaw\fR is the same as \fBTcl_Read\fR but does not
713 compensate for stacking. While \fBTcl_Read\fR (and the other functions
714 in the API) always get their data from the topmost channel in the
715 stack the supplied channel is part of, \fBTcl_ReadRaw\fR does
716 not. Thus this function is \fBonly\fR usable for transformational
717 channel drivers, i.e. drivers used in the middle of a stack of
718 channels, to move data from the channel below into the transformation.
720 .SH "TCL_GETSOBJ AND TCL_GETS"
722 \fBTcl_GetsObj\fR consumes bytes from \fIchannel\fR, converting the bytes to
723 UTF-8 based on the channel's encoding, until a full line of input has been
724 seen. If the channel's encoding is \fBbinary\fR, each byte read from the
725 channel is treated as an individual Unicode character. All of the
726 characters of the line except for the terminating end-of-line character(s)
727 are appended to \fIlineObjPtr\fR's string representation. The end-of-line
728 character(s) are read and discarded.
730 If a line was successfully read, the return value is greater than or equal
731 to zero and indicates the number of bytes stored in \fIlineObjPtr\fR. If an
732 error occurs, \fBTcl_GetsObj\fR returns \-1 and records a POSIX error code
733 that can be retrieved with \fBTcl_GetErrno\fR. \fBTcl_GetsObj\fR also
734 returns \-1 if the end of the file is reached; the \fBTcl_Eof\fR procedure
735 can be used to distinguish an error from an end-of-file condition.
737 If the channel is in nonblocking mode, the return value can also be \-1 if
738 no data was available or the data that was available did not contain an
739 end-of-line character. When \-1 is returned, the \fBTcl_InputBlocked\fR
740 procedure may be invoked to determine if the channel is blocked because
741 of input unavailability.
743 \fBTcl_Gets\fR is the same as \fBTcl_GetsObj\fR except the resulting
744 characters are appended to the dynamic string given by
745 \fIlineRead\fR rather than a Tcl object.
749 \fBTcl_Ungets\fR is used to add data to the input queue of a channel,
750 at either the head or tail of the queue. The pointer \fIinput\fR points
751 to the data that is to be added. The length of the input to add is given
752 by \fIinputLen\fR. A non-zero value of \fIaddAtEnd\fR indicates that the
753 data is to be added at the end of queue; otherwise it will be added at the
754 head of the queue. If \fIchannel\fR has a "sticky" EOF set, no data will be
755 added to the input queue. \fBTcl_Ungets\fR returns \fIinputLen\fR or
756 -1 if an error occurs.
758 .SH "TCL_WRITECHARS, TCL_WRITEOBJ, AND TCL_WRITE"
760 \fBTcl_WriteChars\fR accepts \fIbytesToWrite\fR bytes of character data at
761 \fIcharBuf\fR. The UTF-8 characters in the buffer are converted to the
762 channel's encoding and queued for output to \fIchannel\fR. If
763 \fIbytesToWrite\fR is negative, \fBTcl_WriteChars\fR expects \fIcharBuf\fR
764 to be null-terminated and it outputs everything up to the null.
766 Data queued for output may not appear on the output device immediately, due
767 to internal buffering. If the data should appear immediately, call
768 \fBTcl_Flush\fR after the call to \fBTcl_WriteChars\fR, or set the
769 \fB\-buffering\fR option on the channel to \fBnone\fR. If you wish the data
770 to appear as soon as a complete line is accepted for output, set the
771 \fB\-buffering\fR option on the channel to \fBline\fR mode.
773 The return value of \fBTcl_WriteChars\fR is a count of how many bytes were
774 accepted for output to the channel. This is either greater than zero to
775 indicate success or \-1 to indicate that an error occurred. If an error
776 occurs, \fBTcl_WriteChars\fR records a POSIX error code that may be
777 retrieved with \fBTcl_GetErrno\fR.
779 Newline characters in the output data are translated to platform-specific
780 end-of-line sequences according to the \fB\-translation\fR option for the
781 channel. This is done even if the channel has no encoding.
783 \fBTcl_WriteObj\fR is similar to \fBTcl_WriteChars\fR except it
784 accepts a Tcl object whose contents will be output to the channel. The
785 UTF-8 characters in \fIwriteObjPtr\fR's string representation are converted
786 to the channel's encoding and queued for output to \fIchannel\fR.
787 As a performance optimization, when writing to a channel with the encoding
788 \fBbinary\fR, UTF-8 characters are not converted as they are written.
789 Instead, the bytes in \fIwriteObjPtr\fR's internal representation as a
790 byte-array object are written to the channel. The byte-array representation
791 of the object will be constructed if it is needed. In this way,
792 byte-oriented data can be read from a channel, manipulated by calling
793 \fBTcl_GetByteArrayFromObj\fR and related functions, and then written to a
794 channel without the expense of ever converting to or from UTF-8.
796 \fBTcl_Write\fR is similar to \fBTcl_WriteChars\fR except that it doesn't do
797 encoding conversions, regardless of the channel's encoding. It is
798 deprecated and exists for backwards compatibility with non-internationalized
799 Tcl extensions. It accepts \fIbytesToWrite\fR bytes of data at
800 \fIbyteBuf\fR and queues them for output to \fIchannel\fR. If
801 \fIbytesToWrite\fR is negative, \fBTcl_Write\fR expects \fIbyteBuf\fR to be
802 null-terminated and it outputs everything up to the null.
804 \fBTcl_WriteRaw\fR is the same as \fBTcl_Write\fR but does not
805 compensate for stacking. While \fBTcl_Write\fR (and the other
806 functions in the API) always feed their input to the topmost channel
807 in the stack the supplied channel is part of, \fBTcl_WriteRaw\fR does
808 not. Thus this function is \fBonly\fR usable for transformational
809 channel drivers, i.e. drivers used in the middle of a stack of
810 channels, to move data from the transformation into the channel below
816 \fBTcl_Flush\fR causes all of the buffered output data for \fIchannel\fR
817 to be written to its underlying file or device as soon as possible.
818 If the channel is in blocking mode, the call does not return until
819 all the buffered data has been sent to the channel or some error occurred.
820 The call returns immediately if the channel is nonblocking; it starts
821 a background flush that will write the buffered data to the channel
822 eventually, as fast as the channel is able to absorb it.
824 The return value is normally \fBTCL_OK\fR.
825 If an error occurs, \fBTcl_Flush\fR returns \fBTCL_ERROR\fR and
826 records a POSIX error code that can be retrieved with \fBTcl_GetErrno\fR.
830 \fBTcl_Seek\fR moves the access point in \fIchannel\fR where subsequent
831 data will be read or written. Buffered output is flushed to the channel and
832 buffered input is discarded, prior to the seek operation.
834 \fBTcl_Seek\fR normally returns the new access point.
835 If an error occurs, \fBTcl_Seek\fR returns \-1 and records a POSIX error
836 code that can be retrieved with \fBTcl_GetErrno\fR.
837 After an error, the access point may or may not have been moved.
841 \fBTcl_Tell\fR returns the current access point for a channel. The returned
842 value is \-1 if the channel does not support seeking.
844 .SH TCL_GETCHANNELOPTION
846 \fBTcl_GetChannelOption\fR retrieves, in \fIoptionValue\fR, the value of one of
847 the options currently in effect for a channel, or a list of all options and
848 their values. The \fIchannel\fR argument identifies the channel for which
849 to query an option or retrieve all options and their values.
850 If \fIoptionName\fR is not NULL, it is the name of the
851 option to query; the option's value is copied to the Tcl dynamic string
852 denoted by \fIoptionValue\fR. If
853 \fIoptionName\fR is NULL, the function stores an alternating list of option
854 names and their values in \fIoptionValue\fR, using a series of calls to
855 \fBTcl_DStringAppendElement\fR. The various preexisting options and
856 their possible values are described in the manual entry for the Tcl
857 \fBfconfigure\fR command. Other options can be added by each channel type.
858 These channel type specific options are described in the manual entry for
859 the Tcl command that creates a channel of that type; for example, the
860 additional options for TCP based channels are described in the manual entry
861 for the Tcl \fBsocket\fR command.
862 The procedure normally returns \fBTCL_OK\fR. If an error occurs, it returns
863 \fBTCL_ERROR\fR and calls \fBTcl_SetErrno\fR to store an appropriate POSIX
866 .SH TCL_SETCHANNELOPTION
868 \fBTcl_SetChannelOption\fR sets a new value \fInewValue\fR
869 for an option \fIoptionName\fR on \fIchannel\fR.
870 The procedure normally returns \fBTCL_OK\fR. If an error occurs,
871 it returns \fBTCL_ERROR\fR; in addition, if \fIinterp\fR is non-NULL,
872 \fBTcl_SetChannelOption\fR leaves an error message in the interpreter's result.
876 \fBTcl_Eof\fR returns a nonzero value if \fIchannel\fR encountered
877 an end of file during the last input operation.
881 \fBTcl_InputBlocked\fR returns a nonzero value if \fIchannel\fR is in
882 nonblocking mode and the last input operation returned less data than
883 requested because there was insufficient data available.
884 The call always returns zero if the channel is in blocking mode.
886 .SH TCL_INPUTBUFFERED
888 \fBTcl_InputBuffered\fR returns the number of bytes of input currently
889 buffered in the internal buffers for a channel. If the channel is not open
890 for reading, this function always returns zero.
892 .SH TCL_OUTPUTBUFFERED
894 \fBTcl_OutputBuffered\fR returns the number of bytes of output
895 currently buffered in the internal buffers for a channel. If the
896 channel is not open for writing, this function always returns zero.
899 .SH "PLATFORM ISSUES"
901 The handles returned from \fBTcl_GetChannelHandle\fR depend on the
902 platform and the channel type. On Unix platforms, the handle is
903 always a Unix file descriptor as returned from the \fBopen\fR system
904 call. On Windows platforms, the handle is a file \fBHANDLE\fR when
905 the channel was created with \fBTcl_OpenFileChannel\fR,
906 \fBTcl_OpenCommandChannel\fR, or \fBTcl_MakeFileChannel\fR. Other
907 channel types may return a different type of handle on Windows
908 platforms. On the Macintosh platform, the handle is a file reference
909 number as returned from \fBHOpenDF\fR.
912 DString(3), fconfigure(n), filename(n), fopen(3), Tcl_CreateChannel(3)
915 access point, blocking, buffered I/O, channel, channel driver, end of file,
916 flush, input, nonblocking, output, read, seek, write
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