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diff --git a/tcl8.6/doc/OpenFileChnl.3 b/tcl8.6/doc/OpenFileChnl.3 new file mode 100644 index 0000000..582ff4b --- /dev/null +++ b/tcl8.6/doc/OpenFileChnl.3 @@ -0,0 +1,648 @@ +'\" +'\" Copyright (c) 1996-1997 Sun Microsystems, Inc. +'\" +'\" See the file "license.terms" for information on usage and redistribution +'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. +'\" +.TH Tcl_OpenFileChannel 3 8.3 Tcl "Tcl Library Procedures" +.so man.macros +.BS +'\" Note: do not modify the .SH NAME line immediately below! +.SH NAME +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_TruncateChannel, Tcl_GetChannelOption, Tcl_SetChannelOption, Tcl_Eof, Tcl_InputBlocked, Tcl_InputBuffered, Tcl_OutputBuffered, Tcl_Ungets, Tcl_ReadRaw, Tcl_WriteRaw \- buffered I/O facilities using channels +.SH SYNOPSIS +.nf +\fB#include <tcl.h>\fR +.sp +Tcl_Channel +\fBTcl_OpenFileChannel\fR(\fIinterp, fileName, mode, permissions\fR) +.sp +Tcl_Channel +\fBTcl_OpenCommandChannel\fR(\fIinterp, argc, argv, flags\fR) +.sp +Tcl_Channel +\fBTcl_MakeFileChannel\fR(\fIhandle, readOrWrite\fR) +.sp +Tcl_Channel +\fBTcl_GetChannel\fR(\fIinterp, channelName, modePtr\fR) +.sp +int +\fBTcl_GetChannelNames\fR(\fIinterp\fR) +.sp +int +\fBTcl_GetChannelNamesEx\fR(\fIinterp, pattern\fR) +.sp +void +\fBTcl_RegisterChannel\fR(\fIinterp, channel\fR) +.sp +int +\fBTcl_UnregisterChannel\fR(\fIinterp, channel\fR) +.sp +int +\fBTcl_DetachChannel\fR(\fIinterp, channel\fR) +.sp +int +\fBTcl_IsStandardChannel\fR(\fIchannel\fR) +.sp +int +\fBTcl_Close\fR(\fIinterp, channel\fR) +.sp +int +\fBTcl_ReadChars\fR(\fIchannel, readObjPtr, charsToRead, appendFlag\fR) +.sp +int +\fBTcl_Read\fR(\fIchannel, readBuf, bytesToRead\fR) +.sp +int +\fBTcl_GetsObj\fR(\fIchannel, lineObjPtr\fR) +.sp +int +\fBTcl_Gets\fR(\fIchannel, lineRead\fR) +.sp +int +\fBTcl_Ungets\fR(\fIchannel, input, inputLen, addAtEnd\fR) +.sp +int +\fBTcl_WriteObj\fR(\fIchannel, writeObjPtr\fR) +.sp +int +\fBTcl_WriteChars\fR(\fIchannel, charBuf, bytesToWrite\fR) +.sp +int +\fBTcl_Write\fR(\fIchannel, byteBuf, bytesToWrite\fR) +.sp +int +\fBTcl_ReadRaw\fR(\fIchannel, readBuf, bytesToRead\fR) +.sp +int +\fBTcl_WriteRaw\fR(\fIchannel, byteBuf, bytesToWrite\fR) +.sp +int +\fBTcl_Eof\fR(\fIchannel\fR) +.sp +int +\fBTcl_Flush\fR(\fIchannel\fR) +.sp +int +\fBTcl_InputBlocked\fR(\fIchannel\fR) +.sp +int +\fBTcl_InputBuffered\fR(\fIchannel\fR) +.sp +int +\fBTcl_OutputBuffered\fR(\fIchannel\fR) +.sp +Tcl_WideInt +\fBTcl_Seek\fR(\fIchannel, offset, seekMode\fR) +.sp +Tcl_WideInt +\fBTcl_Tell\fR(\fIchannel\fR) +.sp +int +\fBTcl_TruncateChannel\fR(\fIchannel, length\fR) +.sp +int +\fBTcl_GetChannelOption\fR(\fIinterp, channel, optionName, optionValue\fR) +.sp +int +\fBTcl_SetChannelOption\fR(\fIinterp, channel, optionName, newValue\fR) +.sp +.SH ARGUMENTS +.AS Tcl_DString *channelName in/out +.AP Tcl_Interp *interp in +Used for error reporting and to look up a channel registered in it. +.AP "const char" *fileName in +The name of a local or network file. +.AP "const char" *mode in +Specifies how the file is to be accessed. May have any of the values +allowed for the \fImode\fR argument to the Tcl \fBopen\fR command. +.AP int permissions in +POSIX-style permission flags such as 0644. If a new file is created, these +permissions will be set on the created file. +.AP int argc in +The number of elements in \fIargv\fR. +.AP "const char" **argv in +Arguments for constructing a command pipeline. These values have the same +meaning as the non-switch arguments to the Tcl \fBexec\fR command. +.AP int flags in +Specifies the disposition of the stdio handles in pipeline: OR-ed +combination of \fBTCL_STDIN\fR, \fBTCL_STDOUT\fR, \fBTCL_STDERR\fR, and +\fBTCL_ENFORCE_MODE\fR. If \fBTCL_STDIN\fR is set, stdin for the first child +in the pipe is the pipe channel, otherwise it is the same as the standard +input of the invoking process; likewise for \fBTCL_STDOUT\fR and +\fBTCL_STDERR\fR. If \fBTCL_ENFORCE_MODE\fR is not set, then the pipe can +redirect stdio handles to override the stdio handles for which +\fBTCL_STDIN\fR, \fBTCL_STDOUT\fR and \fBTCL_STDERR\fR have been set. If it +is set, then such redirections cause an error. +.AP ClientData handle in +Operating system specific handle for I/O to a file. For Unix this is a +file descriptor, for Windows it is a HANDLE. +.AP int readOrWrite in +OR-ed combination of \fBTCL_READABLE\fR and \fBTCL_WRITABLE\fR to indicate +what operations are valid on \fIhandle\fR. +.AP "const char" *channelName in +The name of the channel. +.AP int *modePtr out +Points at an integer variable that will receive an OR-ed combination of +\fBTCL_READABLE\fR and \fBTCL_WRITABLE\fR denoting whether the channel is +open for reading and writing. +.AP "const char" *pattern in +The pattern to match on, passed to Tcl_StringMatch, or NULL. +.AP Tcl_Channel channel in +A Tcl channel for input or output. Must have been the return value +from a procedure such as \fBTcl_OpenFileChannel\fR. +.AP Tcl_Obj *readObjPtr in/out +A pointer to a Tcl value in which to store the characters read from the +channel. +.AP int charsToRead in +The number of characters to read from the channel. If the channel's encoding +is \fBbinary\fR, this is equivalent to the number of bytes to read from the +channel. +.AP int appendFlag in +If non-zero, data read from the channel will be appended to the value. +Otherwise, the data will replace the existing contents of the value. +.AP char *readBuf out +A buffer in which to store the bytes read from the channel. +.AP int bytesToRead in +The number of bytes to read from the channel. The buffer \fIreadBuf\fR must +be large enough to hold this many bytes. +.AP Tcl_Obj *lineObjPtr in/out +A pointer to a Tcl value in which to store the line read from the +channel. The line read will be appended to the current value of the +value. +.AP Tcl_DString *lineRead in/out +A pointer to a Tcl dynamic string in which to store the line read from the +channel. Must have been initialized by the caller. The line read will be +appended to any data already in the dynamic string. +.AP "const char" *input in +The input to add to a channel buffer. +.AP int inputLen in +Length of the input +.AP int addAtEnd in +Flag indicating whether the input should be added to the end or +beginning of the channel buffer. +.AP Tcl_Obj *writeObjPtr in +A pointer to a Tcl value whose contents will be output to the channel. +.AP "const char" *charBuf in +A buffer containing the characters to output to the channel. +.AP "const char" *byteBuf in +A buffer containing the bytes to output to the channel. +.AP int bytesToWrite in +The number of bytes to consume from \fIcharBuf\fR or \fIbyteBuf\fR and +output to the channel. +.AP Tcl_WideInt offset in +How far to move the access point in the channel at which the next input or +output operation will be applied, measured in bytes from the position +given by \fIseekMode\fR. May be either positive or negative. +.AP int seekMode in +Relative to which point to seek; used with \fIoffset\fR to calculate the new +access point for the channel. Legal values are \fBSEEK_SET\fR, +\fBSEEK_CUR\fR, and \fBSEEK_END\fR. +.AP Tcl_WideInt length in +The (non-negative) length to truncate the channel the channel to. +.AP "const char" *optionName in +The name of an option applicable to this channel, such as \fB\-blocking\fR. +May have any of the values accepted by the \fBfconfigure\fR command. +.AP Tcl_DString *optionValue in +Where to store the value of an option or a list of all options and their +values. Must have been initialized by the caller. +.AP "const char" *newValue in +New value for the option given by \fIoptionName\fR. +.BE +.SH DESCRIPTION +.PP +The Tcl channel mechanism provides a device-independent and +platform-independent mechanism for performing buffered input +and output operations on a variety of file, socket, and device +types. +The channel mechanism is extensible to new channel types, by +providing a low-level channel driver for the new type; the channel driver +interface is described in the manual entry for \fBTcl_CreateChannel\fR. The +channel mechanism provides a buffering scheme modeled after +Unix's standard I/O, and it also allows for nonblocking I/O on +channels. +.PP +The procedures described in this manual entry comprise the C APIs of the +generic layer of the channel architecture. For a description of the channel +driver architecture and how to implement channel drivers for new types of +channels, see the manual entry for \fBTcl_CreateChannel\fR. +.SH TCL_OPENFILECHANNEL +.PP +\fBTcl_OpenFileChannel\fR opens a file specified by \fIfileName\fR and +returns a channel handle that can be used to perform input and output on +the file. This API is modeled after the \fBfopen\fR procedure of +the Unix standard I/O library. +The syntax and meaning of all arguments is similar to those +given in the Tcl \fBopen\fR command when opening a file. +If an error occurs while opening the channel, \fBTcl_OpenFileChannel\fR +returns NULL and records a POSIX error code that can be +retrieved with \fBTcl_GetErrno\fR. +In addition, if \fIinterp\fR is non-NULL, \fBTcl_OpenFileChannel\fR +leaves an error message in \fIinterp\fR's result after any error. +As of Tcl 8.4, the value-based API \fBTcl_FSOpenFileChannel\fR should +be used in preference to \fBTcl_OpenFileChannel\fR wherever possible. +.PP +The newly created channel is not registered in the supplied interpreter; to +register it, use \fBTcl_RegisterChannel\fR, described below. +If one of the standard channels, \fBstdin\fR, \fBstdout\fR or \fBstderr\fR was +previously closed, the act of creating the new channel also assigns it as a +replacement for the standard channel. +.SH TCL_OPENCOMMANDCHANNEL +.PP +\fBTcl_OpenCommandChannel\fR provides a C-level interface to the +functions of the \fBexec\fR and \fBopen\fR commands. +It creates a sequence of subprocesses specified +by the \fIargv\fR and \fIargc\fR arguments and returns a channel that can +be used to communicate with these subprocesses. +The \fIflags\fR argument indicates what sort of communication will +exist with the command pipeline. +.PP +If the \fBTCL_STDIN\fR flag is set then the standard input for the +first subprocess will be tied to the channel: writing to the channel +will provide input to the subprocess. If \fBTCL_STDIN\fR is not set, +then standard input for the first subprocess will be the same as this +application's standard input. If \fBTCL_STDOUT\fR is set then +standard output from the last subprocess can be read from the channel; +otherwise it goes to this application's standard output. If +\fBTCL_STDERR\fR is set, standard error output for all subprocesses is +returned to the channel and results in an error when the channel is +closed; otherwise it goes to this application's standard error. If +\fBTCL_ENFORCE_MODE\fR is not set, then \fIargc\fR and \fIargv\fR can +redirect the stdio handles to override \fBTCL_STDIN\fR, +\fBTCL_STDOUT\fR, and \fBTCL_STDERR\fR; if it is set, then it is an +error for argc and argv to override stdio channels for which +\fBTCL_STDIN\fR, \fBTCL_STDOUT\fR, and \fBTCL_STDERR\fR have been set. +.PP +If an error occurs while opening the channel, \fBTcl_OpenCommandChannel\fR +returns NULL and records a POSIX error code that can be retrieved with +\fBTcl_GetErrno\fR. +In addition, \fBTcl_OpenCommandChannel\fR leaves an error message in +the interpreter's result if \fIinterp\fR is not NULL. +.PP +The newly created channel is not registered in the supplied interpreter; to +register it, use \fBTcl_RegisterChannel\fR, described below. +If one of the standard channels, \fBstdin\fR, \fBstdout\fR or \fBstderr\fR was +previously closed, the act of creating the new channel also assigns it as a +replacement for the standard channel. +.SH TCL_MAKEFILECHANNEL +.PP +\fBTcl_MakeFileChannel\fR makes a \fBTcl_Channel\fR from an existing, +platform-specific, file handle. +The newly created channel is not registered in the supplied interpreter; to +register it, use \fBTcl_RegisterChannel\fR, described below. +If one of the standard channels, \fBstdin\fR, \fBstdout\fR or \fBstderr\fR was +previously closed, the act of creating the new channel also assigns it as a +replacement for the standard channel. +.SH TCL_GETCHANNEL +.PP +\fBTcl_GetChannel\fR returns a channel given the \fIchannelName\fR used to +create it with \fBTcl_CreateChannel\fR and a pointer to a Tcl interpreter in +\fIinterp\fR. If a channel by that name is not registered in that interpreter, +the procedure returns NULL. If the \fImodePtr\fR argument is not NULL, it +points at an integer variable that will receive an OR-ed combination of +\fBTCL_READABLE\fR and \fBTCL_WRITABLE\fR describing whether the channel is +open for reading and writing. +.PP +\fBTcl_GetChannelNames\fR and \fBTcl_GetChannelNamesEx\fR write the +names of the registered channels to the interpreter's result as a +list value. \fBTcl_GetChannelNamesEx\fR will filter these names +according to the \fIpattern\fR. If \fIpattern\fR is NULL, then it +will not do any filtering. The return value is \fBTCL_OK\fR if no +errors occurred writing to the result, otherwise it is \fBTCL_ERROR\fR, +and the error message is left in the interpreter's result. +.SH TCL_REGISTERCHANNEL +.PP +\fBTcl_RegisterChannel\fR adds a channel to the set of channels accessible +in \fIinterp\fR. After this call, Tcl programs executing in that +interpreter can refer to the channel in input or output operations using +the name given in the call to \fBTcl_CreateChannel\fR. After this call, +the channel becomes the property of the interpreter, and the caller should +not call \fBTcl_Close\fR for the channel; the channel will be closed +automatically when it is unregistered from the interpreter. +.PP +Code executing outside of any Tcl interpreter can call +\fBTcl_RegisterChannel\fR with \fIinterp\fR as NULL, to indicate that it +wishes to hold a reference to this channel. Subsequently, the channel can +be registered in a Tcl interpreter and it will only be closed when the +matching number of calls to \fBTcl_UnregisterChannel\fR have been made. +This allows code executing outside of any interpreter to safely hold a +reference to a channel that is also registered in a Tcl interpreter. +.PP +This procedure interacts with the code managing the standard +channels. If no standard channels were initialized before the first +call to \fBTcl_RegisterChannel\fR, they will get initialized by that +call. See \fBTcl_StandardChannels\fR for a general treatise about +standard channels and the behavior of the Tcl library with regard to +them. +.SH TCL_UNREGISTERCHANNEL +.PP +\fBTcl_UnregisterChannel\fR removes a channel from the set of channels +accessible in \fIinterp\fR. After this call, Tcl programs will no longer be +able to use the channel's name to refer to the channel in that interpreter. +If this operation removed the last registration of the channel in any +interpreter, the channel is also closed and destroyed. +.PP +Code not associated with a Tcl interpreter can call +\fBTcl_UnregisterChannel\fR with \fIinterp\fR as NULL, to indicate to Tcl +that it no longer holds a reference to that channel. If this is the last +reference to the channel, it will now be closed. \fBTcl_UnregisterChannel\fR +is very similar to \fBTcl_DetachChannel\fR except that it will also +close the channel if no further references to it exist. +.SH TCL_DETACHCHANNEL +.PP +\fBTcl_DetachChannel\fR removes a channel from the set of channels +accessible in \fIinterp\fR. After this call, Tcl programs will no longer be +able to use the channel's name to refer to the channel in that interpreter. +Beyond that, this command has no further effect. It cannot be used on +the standard channels (\fBstdout\fR, \fBstderr\fR, \fBstdin\fR), and will return +\fBTCL_ERROR\fR if passed one of those channels. +.PP +Code not associated with a Tcl interpreter can call +\fBTcl_DetachChannel\fR with \fIinterp\fR as NULL, to indicate to Tcl +that it no longer holds a reference to that channel. If this is the last +reference to the channel, unlike \fBTcl_UnregisterChannel\fR, +it will not be closed. +.SH TCL_ISSTANDARDCHANNEL +.PP +\fBTcl_IsStandardChannel\fR tests whether a channel is one of the +three standard channels, \fBstdin\fR, \fBstdout\fR or \fBstderr\fR. +If so, it returns 1, otherwise 0. +.PP +No attempt is made to check whether the given channel or the standard +channels are initialized or otherwise valid. +.SH TCL_CLOSE +.PP +\fBTcl_Close\fR destroys the channel \fIchannel\fR, which must denote a +currently open channel. The channel should not be registered in any +interpreter when \fBTcl_Close\fR is called. Buffered output is flushed to +the channel's output device prior to destroying the channel, and any +buffered input is discarded. If this is a blocking channel, the call does +not return until all buffered data is successfully sent to the channel's +output device. If this is a nonblocking channel and there is buffered +output that cannot be written without blocking, the call returns +immediately; output is flushed in the background and the channel will be +closed once all of the buffered data has been output. In this case errors +during flushing are not reported. +.PP +If the channel was closed successfully, \fBTcl_Close\fR returns \fBTCL_OK\fR. +If an error occurs, \fBTcl_Close\fR returns \fBTCL_ERROR\fR and records a +POSIX error code that can be retrieved with \fBTcl_GetErrno\fR. +If the channel is being closed synchronously and an error occurs during +closing of the channel and \fIinterp\fR is not NULL, an error message is +left in the interpreter's result. +.PP +Note: it is not safe to call \fBTcl_Close\fR on a channel that has been +registered using \fBTcl_RegisterChannel\fR; see the documentation for +\fBTcl_RegisterChannel\fR, above, for details. If the channel has ever +been given as the \fBchan\fR argument in a call to +\fBTcl_RegisterChannel\fR, you should instead use +\fBTcl_UnregisterChannel\fR, which will internally call \fBTcl_Close\fR +when all calls to \fBTcl_RegisterChannel\fR have been matched by +corresponding calls to \fBTcl_UnregisterChannel\fR. +.SH "TCL_READCHARS AND TCL_READ" +.PP +\fBTcl_ReadChars\fR consumes bytes from \fIchannel\fR, converting the bytes +to UTF-8 based on the channel's encoding and storing the produced data in +\fIreadObjPtr\fR's string representation. The return value of +\fBTcl_ReadChars\fR is the number of characters, up to \fIcharsToRead\fR, +that were stored in \fIreadObjPtr\fR. If an error occurs while reading, the +return value is \-1 and \fBTcl_ReadChars\fR records a POSIX error code that +can be retrieved with \fBTcl_GetErrno\fR. +.PP +Setting \fIcharsToRead\fR to \fB\-1\fR will cause the command to read +all characters currently available (non-blocking) or everything until +eof (blocking mode). +.PP +The return value may be smaller than the value to read, indicating that less +data than requested was available. This is called a \fIshort read\fR. In +blocking mode, this can only happen on an end-of-file. In nonblocking mode, +a short read can also occur if there is not enough input currently +available: \fBTcl_ReadChars\fR returns a short count rather than waiting +for more data. +.PP +If the channel is in blocking mode, a return value of zero indicates an +end-of-file condition. If the channel is in nonblocking mode, a return +value of zero indicates either that no input is currently available or an +end-of-file condition. Use \fBTcl_Eof\fR and \fBTcl_InputBlocked\fR to tell +which of these conditions actually occurred. +.PP +\fBTcl_ReadChars\fR translates the various end-of-line representations into +the canonical \fB\en\fR internal representation according to the current +end-of-line recognition mode. End-of-line recognition and the various +platform-specific modes are described in the manual entry for the Tcl +\fBfconfigure\fR command. +.PP +As a performance optimization, when reading from a channel with the encoding +\fBbinary\fR, the bytes are not converted to UTF-8 as they are read. +Instead, they are stored in \fIreadObjPtr\fR's internal representation as a +byte-array value. The string representation of this value will only be +constructed if it is needed (e.g., because of a call to +\fBTcl_GetStringFromObj\fR). In this way, byte-oriented data can be read +from a channel, manipulated by calling \fBTcl_GetByteArrayFromObj\fR and +related functions, and then written to a channel without the expense of ever +converting to or from UTF-8. +.PP +\fBTcl_Read\fR is similar to \fBTcl_ReadChars\fR, except that it does not do +encoding conversions, regardless of the channel's encoding. It is deprecated +and exists for backwards compatibility with non-internationalized Tcl +extensions. It consumes bytes from \fIchannel\fR and stores them in +\fIreadBuf\fR, performing end-of-line translations on the way. The return value +of \fBTcl_Read\fR is the number of bytes, up to \fIbytesToRead\fR, written in +\fIreadBuf\fR. The buffer produced by \fBTcl_Read\fR is not null-terminated. +Its contents are valid from the zeroth position up to and excluding the +position indicated by the return value. +.PP +\fBTcl_ReadRaw\fR is the same as \fBTcl_Read\fR but does not +compensate for stacking. While \fBTcl_Read\fR (and the other functions +in the API) always get their data from the topmost channel in the +stack the supplied channel is part of, \fBTcl_ReadRaw\fR does +not. Thus this function is \fBonly\fR usable for transformational +channel drivers, i.e. drivers used in the middle of a stack of +channels, to move data from the channel below into the transformation. +.SH "TCL_GETSOBJ AND TCL_GETS" +.PP +\fBTcl_GetsObj\fR consumes bytes from \fIchannel\fR, converting the bytes to +UTF-8 based on the channel's encoding, until a full line of input has been +seen. If the channel's encoding is \fBbinary\fR, each byte read from the +channel is treated as an individual Unicode character. All of the +characters of the line except for the terminating end-of-line character(s) +are appended to \fIlineObjPtr\fR's string representation. The end-of-line +character(s) are read and discarded. +.PP +If a line was successfully read, the return value is greater than or equal +to zero and indicates the number of bytes stored in \fIlineObjPtr\fR. If an +error occurs, \fBTcl_GetsObj\fR returns \-1 and records a POSIX error code +that can be retrieved with \fBTcl_GetErrno\fR. \fBTcl_GetsObj\fR also +returns \-1 if the end of the file is reached; the \fBTcl_Eof\fR procedure +can be used to distinguish an error from an end-of-file condition. +.PP +If the channel is in nonblocking mode, the return value can also be \-1 if +no data was available or the data that was available did not contain an +end-of-line character. When \-1 is returned, the \fBTcl_InputBlocked\fR +procedure may be invoked to determine if the channel is blocked because +of input unavailability. +.PP +\fBTcl_Gets\fR is the same as \fBTcl_GetsObj\fR except the resulting +characters are appended to the dynamic string given by +\fIlineRead\fR rather than a Tcl value. +.SH "TCL_UNGETS" +.PP +\fBTcl_Ungets\fR is used to add data to the input queue of a channel, +at either the head or tail of the queue. The pointer \fIinput\fR points +to the data that is to be added. The length of the input to add is given +by \fIinputLen\fR. A non-zero value of \fIaddAtEnd\fR indicates that the +data is to be added at the end of queue; otherwise it will be added at the +head of the queue. If \fIchannel\fR has a +.QW sticky +EOF set, no data will be +added to the input queue. \fBTcl_Ungets\fR returns \fIinputLen\fR or +\-1 if an error occurs. +.SH "TCL_WRITECHARS, TCL_WRITEOBJ, AND TCL_WRITE" +.PP +\fBTcl_WriteChars\fR accepts \fIbytesToWrite\fR bytes of character data at +\fIcharBuf\fR. The UTF-8 characters in the buffer are converted to the +channel's encoding and queued for output to \fIchannel\fR. If +\fIbytesToWrite\fR is negative, \fBTcl_WriteChars\fR expects \fIcharBuf\fR +to be null-terminated and it outputs everything up to the null. +.PP +Data queued for output may not appear on the output device immediately, due +to internal buffering. If the data should appear immediately, call +\fBTcl_Flush\fR after the call to \fBTcl_WriteChars\fR, or set the +\fB\-buffering\fR option on the channel to \fBnone\fR. If you wish the data +to appear as soon as a complete line is accepted for output, set the +\fB\-buffering\fR option on the channel to \fBline\fR mode. +.PP +The return value of \fBTcl_WriteChars\fR is a count of how many bytes were +accepted for output to the channel. This is either greater than zero to +indicate success or \-1 to indicate that an error occurred. If an error +occurs, \fBTcl_WriteChars\fR records a POSIX error code that may be +retrieved with \fBTcl_GetErrno\fR. +.PP +Newline characters in the output data are translated to platform-specific +end-of-line sequences according to the \fB\-translation\fR option for the +channel. This is done even if the channel has no encoding. +.PP +\fBTcl_WriteObj\fR is similar to \fBTcl_WriteChars\fR except it +accepts a Tcl value whose contents will be output to the channel. The +UTF-8 characters in \fIwriteObjPtr\fR's string representation are converted +to the channel's encoding and queued for output to \fIchannel\fR. +As a performance optimization, when writing to a channel with the encoding +\fBbinary\fR, UTF-8 characters are not converted as they are written. +Instead, the bytes in \fIwriteObjPtr\fR's internal representation as a +byte-array value are written to the channel. The byte-array representation +of the value will be constructed if it is needed. In this way, +byte-oriented data can be read from a channel, manipulated by calling +\fBTcl_GetByteArrayFromObj\fR and related functions, and then written to a +channel without the expense of ever converting to or from UTF-8. +.PP +\fBTcl_Write\fR is similar to \fBTcl_WriteChars\fR except that it does not do +encoding conversions, regardless of the channel's encoding. It is +deprecated and exists for backwards compatibility with non-internationalized +Tcl extensions. It accepts \fIbytesToWrite\fR bytes of data at +\fIbyteBuf\fR and queues them for output to \fIchannel\fR. If +\fIbytesToWrite\fR is negative, \fBTcl_Write\fR expects \fIbyteBuf\fR to be +null-terminated and it outputs everything up to the null. +.PP +\fBTcl_WriteRaw\fR is the same as \fBTcl_Write\fR but does not +compensate for stacking. While \fBTcl_Write\fR (and the other +functions in the API) always feed their input to the topmost channel +in the stack the supplied channel is part of, \fBTcl_WriteRaw\fR does +not. Thus this function is \fBonly\fR usable for transformational +channel drivers, i.e. drivers used in the middle of a stack of +channels, to move data from the transformation into the channel below +it. +.SH TCL_FLUSH +.PP +\fBTcl_Flush\fR causes all of the buffered output data for \fIchannel\fR +to be written to its underlying file or device as soon as possible. +If the channel is in blocking mode, the call does not return until +all the buffered data has been sent to the channel or some error occurred. +The call returns immediately if the channel is nonblocking; it starts +a background flush that will write the buffered data to the channel +eventually, as fast as the channel is able to absorb it. +.PP +The return value is normally \fBTCL_OK\fR. +If an error occurs, \fBTcl_Flush\fR returns \fBTCL_ERROR\fR and +records a POSIX error code that can be retrieved with \fBTcl_GetErrno\fR. +.SH TCL_SEEK +.PP +\fBTcl_Seek\fR moves the access point in \fIchannel\fR where subsequent +data will be read or written. Buffered output is flushed to the channel and +buffered input is discarded, prior to the seek operation. +.PP +\fBTcl_Seek\fR normally returns the new access point. +If an error occurs, \fBTcl_Seek\fR returns \-1 and records a POSIX error +code that can be retrieved with \fBTcl_GetErrno\fR. +After an error, the access point may or may not have been moved. +.SH TCL_TELL +.PP +\fBTcl_Tell\fR returns the current access point for a channel. The returned +value is \-1 if the channel does not support seeking. +.SH TCL_TRUNCATECHANNEL +.PP +\fBTcl_TruncateChannel\fR truncates the file underlying \fIchannel\fR +to a given \fIlength\fR of bytes. It returns \fBTCL_OK\fR if the +operation succeeded, and \fBTCL_ERROR\fR otherwise. +.SH TCL_GETCHANNELOPTION +.PP +\fBTcl_GetChannelOption\fR retrieves, in \fIoptionValue\fR, the value of one of +the options currently in effect for a channel, or a list of all options and +their values. The \fIchannel\fR argument identifies the channel for which +to query an option or retrieve all options and their values. +If \fIoptionName\fR is not NULL, it is the name of the +option to query; the option's value is copied to the Tcl dynamic string +denoted by \fIoptionValue\fR. If +\fIoptionName\fR is NULL, the function stores an alternating list of option +names and their values in \fIoptionValue\fR, using a series of calls to +\fBTcl_DStringAppendElement\fR. The various preexisting options and +their possible values are described in the manual entry for the Tcl +\fBfconfigure\fR command. Other options can be added by each channel type. +These channel type specific options are described in the manual entry for +the Tcl command that creates a channel of that type; for example, the +additional options for TCP based channels are described in the manual entry +for the Tcl \fBsocket\fR command. +The procedure normally returns \fBTCL_OK\fR. If an error occurs, it returns +\fBTCL_ERROR\fR and calls \fBTcl_SetErrno\fR to store an appropriate POSIX +error code. +.SH TCL_SETCHANNELOPTION +.PP +\fBTcl_SetChannelOption\fR sets a new value \fInewValue\fR +for an option \fIoptionName\fR on \fIchannel\fR. +The procedure normally returns \fBTCL_OK\fR. If an error occurs, +it returns \fBTCL_ERROR\fR; in addition, if \fIinterp\fR is non-NULL, +\fBTcl_SetChannelOption\fR leaves an error message in the interpreter's result. +.SH TCL_EOF +.PP +\fBTcl_Eof\fR returns a nonzero value if \fIchannel\fR encountered +an end of file during the last input operation. +.SH TCL_INPUTBLOCKED +.PP +\fBTcl_InputBlocked\fR returns a nonzero value if \fIchannel\fR is in +nonblocking mode and the last input operation returned less data than +requested because there was insufficient data available. +The call always returns zero if the channel is in blocking mode. +.SH TCL_INPUTBUFFERED +.PP +\fBTcl_InputBuffered\fR returns the number of bytes of input currently +buffered in the internal buffers for a channel. If the channel is not open +for reading, this function always returns zero. +.SH TCL_OUTPUTBUFFERED +.PP +\fBTcl_OutputBuffered\fR returns the number of bytes of output +currently buffered in the internal buffers for a channel. If the +channel is not open for writing, this function always returns zero. +.SH "PLATFORM ISSUES" +.PP +The handles returned from \fBTcl_GetChannelHandle\fR depend on the +platform and the channel type. On Unix platforms, the handle is +always a Unix file descriptor as returned from the \fBopen\fR system +call. On Windows platforms, the handle is a file \fBHANDLE\fR when +the channel was created with \fBTcl_OpenFileChannel\fR, +\fBTcl_OpenCommandChannel\fR, or \fBTcl_MakeFileChannel\fR. Other +channel types may return a different type of handle on Windows +platforms. +.SH "SEE ALSO" +DString(3), fconfigure(n), filename(n), fopen(3), Tcl_CreateChannel(3) +.SH KEYWORDS +access point, blocking, buffered I/O, channel, channel driver, end of file, +flush, input, nonblocking, output, read, seek, write |