- 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_GetChannelOption, Tcl_SetChannelOption, Tcl_Eof, Tcl_InputBlocked, Tcl_InputBuffered, Tcl_OutputBuffered, Tcl_Ungets, Tcl_ReadRaw, Tcl_WriteRaw - buffered I/O facilities using channels
- SYNOPSIS
- ARGUMENTS
- DESCRIPTION
- TCL_OPENFILECHANNEL
- TCL_OPENCOMMANDCHANNEL
- TCL_MAKEFILECHANNEL
- TCL_GETCHANNEL
- TCL_REGISTERCHANNEL
- TCL_UNREGISTERCHANNEL
- TCL_DETACHCHANNEL
- TCL_ISSTANDARDCHANNEL
- TCL_CLOSE
- TCL_READCHARS AND TCL_READ
- TCL_GETSOBJ AND TCL_GETS
- TCL_UNGETS
- TCL_WRITECHARS, TCL_WRITEOBJ, AND TCL_WRITE
- TCL_FLUSH
- TCL_SEEK
- TCL_TELL
- TCL_GETCHANNELOPTION
- TCL_SETCHANNELOPTION
- TCL_EOF
- TCL_INPUTBLOCKED
- TCL_INPUTBUFFERED
- TCL_OUTPUTBUFFERED
- PLATFORM ISSUES
- SEE ALSO
- KEYWORDS
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
#include <tcl.h>
Tcl_Channel
Tcl_OpenFileChannel(interp, fileName, mode, permissions)
Tcl_Channel
Tcl_OpenCommandChannel(interp, argc, argv, flags)
Tcl_Channel
Tcl_MakeFileChannel(handle, readOrWrite)
Tcl_Channel
Tcl_GetChannel(interp, channelName, modePtr)
int
Tcl_GetChannelNames(interp)
int
Tcl_GetChannelNamesEx(interp, pattern)
void
Tcl_RegisterChannel(interp, channel)
int
Tcl_UnregisterChannel(interp, channel)
int
Tcl_DetachChannel(interp, channel)
int
Tcl_IsStandardChannel(channel)
int
Tcl_Close(interp, channel)
int
Tcl_ReadChars(channel, readObjPtr, charsToRead, appendFlag)
int
Tcl_Read(channel, readBuf, bytesToRead)
int
Tcl_GetsObj(channel, lineObjPtr)
int
Tcl_Gets(channel, lineRead)
int
Tcl_Ungets(channel, input, inputLen, addAtEnd)
int
Tcl_WriteObj(channel, writeObjPtr)
int
Tcl_WriteChars(channel, charBuf, bytesToWrite)
int
Tcl_Write(channel, byteBuf, bytesToWrite)
int
Tcl_ReadRaw(channel, readBuf, bytesToRead)
int
Tcl_WriteRaw(channel, byteBuf, bytesToWrite)
int
Tcl_Eof(channel)
int
Tcl_Flush(channel)
int
Tcl_InputBlocked(channel)
int
Tcl_InputBuffered(channel)
int
Tcl_OutputBuffered(channel)
Tcl_WideInt
Tcl_Seek(channel, offset, seekMode)
Tcl_WideInt
Tcl_Tell(channel)
int
Tcl_GetChannelOption(interp, channel, optionName, optionValue)
int
Tcl_SetChannelOption(interp, channel, optionName, newValue)
- Tcl_Interp *interp (in)
-
Used for error reporting and to look up a channel registered in it.
- CONST char *fileName (in)
-
The name of a local or network file.
- CONST char *mode (in)
-
Specifies how the file is to be accessed. May have any of the values
allowed for the mode argument to the Tcl open command.
- 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.
- int argc (in)
-
The number of elements in argv.
- CONST char **argv (in)
-
Arguments for constructing a command pipeline. These values have the same
meaning as the non-switch arguments to the Tcl exec command.
- int flags (in)
-
Specifies the disposition of the stdio handles in pipeline: OR-ed
combination of TCL_STDIN, TCL_STDOUT, TCL_STDERR, and
TCL_ENFORCE_MODE. If TCL_STDIN 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 TCL_STDOUT and
TCL_STDERR. If TCL_ENFORCE_MODE is not set, then the pipe can
redirect stdio handles to override the stdio handles for which
TCL_STDIN, TCL_STDOUT and TCL_STDERR have been set. If it
is set, then such redirections cause an error.
- 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.
- int readOrWrite (in)
-
OR-ed combination of TCL_READABLE and TCL_WRITABLE to indicate
what operations are valid on handle.
- CONST char *channelName (in)
-
The name of the channel.
- int *modePtr (out)
-
Points at an integer variable that will receive an OR-ed combination of
TCL_READABLE and TCL_WRITABLE denoting whether the channel is
open for reading and writing.
- CONST char *pattern (in)
-
The pattern to match on, passed to Tcl_StringMatch, or NULL.
- Tcl_Channel channel (in)
-
A Tcl channel for input or output. Must have been the return value
from a procedure such as Tcl_OpenFileChannel.
- Tcl_Obj *readObjPtr (in/out)
-
A pointer to a Tcl Object in which to store the characters read from the
channel.
- int charsToRead (in)
-
The number of characters to read from the channel. If the channel's encoding
is binary, this is equivalent to the number of bytes to read from the
channel.
- int appendFlag (in)
-
If non-zero, data read from the channel will be appended to the object.
Otherwise, the data will replace the existing contents of the object.
- char *readBuf (out)
-
A buffer in which to store the bytes read from the channel.
- int bytesToRead (in)
-
The number of bytes to read from the channel. The buffer readBuf must
be large enough to hold this many bytes.
- Tcl_Obj *lineObjPtr (in/out)
-
A pointer to a Tcl object in which to store the line read from the
channel. The line read will be appended to the current value of the
object.
- 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.
- CONST char *input (in)
-
The input to add to a channel buffer.
- int inputLen (in)
-
Length of the input
- int addAtEnd (in)
-
Flag indicating whether the input should be added to the end or
beginning of the channel buffer.
- Tcl_Obj *writeObjPtr (in)
-
A pointer to a Tcl Object whose contents will be output to the channel.
- CONST char *charBuf (in)
-
A buffer containing the characters to output to the channel.
- CONST char *byteBuf (in)
-
A buffer containing the bytes to output to the channel.
- int bytesToWrite (in)
-
The number of bytes to consume from charBuf or byteBuf and
output to the channel.
- 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 seekMode. May be either positive or negative.
- int seekMode (in)
-
Relative to which point to seek; used with offset to calculate the new
access point for the channel. Legal values are SEEK_SET,
SEEK_CUR, and SEEK_END.
- CONST char *optionName (in)
-
The name of an option applicable to this channel, such as -blocking.
May have any of the values accepted by the fconfigure command.
- 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.
- CONST char *newValue (in)
-
New value for the option given by optionName.
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 Tcl_CreateChannel. The
channel mechanism provides a buffering scheme modeled after
Unix's standard I/O, and it also allows for nonblocking I/O on
channels.
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 Tcl_CreateChannel.
Tcl_OpenFileChannel opens a file specified by fileName and
returns a channel handle that can be used to perform input and output on
the file. This API is modeled after the fopen procedure of
the Unix standard I/O library.
The syntax and meaning of all arguments is similar to those
given in the Tcl open command when opening a file.
If an error occurs while opening the channel, Tcl_OpenFileChannel
returns NULL and records a POSIX error code that can be
retrieved with Tcl_GetErrno.
In addition, if interp is non-NULL, Tcl_OpenFileChannel
leaves an error message in interp's result after any error.
As of Tcl 8.4, the object-based API Tcl_FSOpenFileChannel should
be used in preference to Tcl_OpenFileChannel wherever possible.
The newly created channel is not registered in the supplied interpreter; to
register it, use Tcl_RegisterChannel, described below.
If one of the standard channels, stdin, stdout or stderr was
previously closed, the act of creating the new channel also assigns it as a
replacement for the standard channel.
Tcl_OpenCommandChannel provides a C-level interface to the
functions of the exec and open commands.
It creates a sequence of subprocesses specified
by the argv and argc arguments and returns a channel that can
be used to communicate with these subprocesses.
The flags argument indicates what sort of communication will
exist with the command pipeline.
If the TCL_STDIN 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 TCL_STDIN is not set,
then standard input for the first subprocess will be the same as this
application's standard input. If TCL_STDOUT 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
TCL_STDERR 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
TCL_ENFORCE_MODE is not set, then argc and argv can
redirect the stdio handles to override TCL_STDIN,
TCL_STDOUT, and TCL_STDERR; if it is set, then it is an
error for argc and argv to override stdio channels for which
TCL_STDIN, TCL_STDOUT, and TCL_STDERR have been set.
If an error occurs while opening the channel, Tcl_OpenCommandChannel
returns NULL and records a POSIX error code that can be retrieved with
Tcl_GetErrno.
In addition, Tcl_OpenCommandChannel leaves an error message in
the interpreter's result if interp is not NULL.
The newly created channel is not registered in the supplied interpreter; to
register it, use Tcl_RegisterChannel, described below.
If one of the standard channels, stdin, stdout or stderr was
previously closed, the act of creating the new channel also assigns it as a
replacement for the standard channel.
Tcl_MakeFileChannel makes a Tcl_Channel from an existing,
platform-specific, file handle.
The newly created channel is not registered in the supplied interpreter; to
register it, use Tcl_RegisterChannel, described below.
If one of the standard channels, stdin, stdout or stderr was
previously closed, the act of creating the new channel also assigns it as a
replacement for the standard channel.
Tcl_GetChannel returns a channel given the channelName used to
create it with Tcl_CreateChannel and a pointer to a Tcl interpreter in
interp. If a channel by that name is not registered in that interpreter,
the procedure returns NULL. If the modePtr argument is not NULL, it
points at an integer variable that will receive an OR-ed combination of
TCL_READABLE and TCL_WRITABLE describing whether the channel is
open for reading and writing.
Tcl_GetChannelNames and Tcl_GetChannelNamesEx write the
names of the registered channels to the interpreter's result as a
list object. Tcl_GetChannelNamesEx will filter these names
according to the pattern. If pattern is NULL, then it
will not do any filtering. The return value is TCL_OK if no
errors occurred writing to the result, otherwise it is TCL_ERROR,
and the error message is left in the interpreter's result.
Tcl_RegisterChannel adds a channel to the set of channels accessible
in interp. 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 Tcl_CreateChannel. After this call,
the channel becomes the property of the interpreter, and the caller should
not call Tcl_Close for the channel; the channel will be closed
automatically when it is unregistered from the interpreter.
Code executing outside of any Tcl interpreter can call
Tcl_RegisterChannel with interp 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 Tcl_UnregisterChannel 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.
This procedure interacts with the code managing the standard
channels. If no standard channels were initialized before the first
call to Tcl_RegisterChannel they will get initialized by that
call. See Tcl_StandardChannels for a general treatise about
standard channels and the behaviour of the Tcl library with regard to
them.
Tcl_UnregisterChannel removes a channel from the set of channels
accessible in interp. 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.
Code not associated with a Tcl interpreter can call
Tcl_UnregisterChannel with interp 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. Tcl_UnregisterChannel
is very similar to Tcl_DetachChannel except that it will also
close the channel if no further references to it exist.
Tcl_DetachChannel removes a channel from the set of channels
accessible in interp. 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 (stdout, stderr, stdin), and will return
TCL_ERROR if passed one of those channels.
Code not associated with a Tcl interpreter can call
Tcl_DetachChannel with interp 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 Tcl_UnregisterChannel,
it will not be closed.
Tcl_IsStandardChannel tests whether a channel is one of the
three standard channels, stdin, stdout or stderr. If so, it returns
1, otherwise 0.
No attempt is made to check whether the given channel or the standard
channels are initialized or otherwise valid.
Tcl_Close destroys the channel channel, which must denote a
currently open channel. The channel should not be registered in any
interpreter when Tcl_Close 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.
If the channel was closed successfully, Tcl_Close returns TCL_OK.
If an error occurs, Tcl_Close returns TCL_ERROR and records a
POSIX error code that can be retrieved with Tcl_GetErrno.
If the channel is being closed synchronously and an error occurs during
closing of the channel and interp is not NULL, an error message is
left in the interpreter's result.
Note: it is not safe to call Tcl_Close on a channel that has been
registered using Tcl_RegisterChannel; see the documentation for
Tcl_RegisterChannel, above, for details. If the channel has ever
been given as the chan argument in a call to
Tcl_RegisterChannel, you should instead use
Tcl_UnregisterChannel, which will internally call Tcl_Close
when all calls to Tcl_RegisterChannel have been matched by
corresponding calls to Tcl_UnregisterChannel.
Tcl_ReadChars consumes bytes from channel, converting the bytes
to UTF-8 based on the channel's encoding and storing the produced data in
readObjPtr's string representation. The return value of
Tcl_ReadChars is the number of characters, up to charsToRead,
that were stored in readObjPtr. If an error occurs while reading, the
return value is -1 and Tcl_ReadChars records a POSIX error code that
can be retrieved with Tcl_GetErrno.
Setting charsToRead to -1 will cause the command to read
all characters currently available (non-blocking) or everything until
eof (blocking mode).
The return value may be smaller than the value to read, indicating that less
data than requested was available. This is called a short read. 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: Tcl_ReadChars returns a short count rather than waiting
for more data.
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 Tcl_Eof and Tcl_InputBlocked to tell
which of these conditions actually occurred.
Tcl_ReadChars translates the various end-of-line representations into
the canonical \n 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
fconfigure command.
As a performance optimization, when reading from a channel with the encoding
binary, the bytes are not converted to UTF-8 as they are read.
Instead, they are stored in readObjPtr's internal representation as a
byte-array object. The string representation of this object will only be
constructed if it is needed (e.g., because of a call to
Tcl_GetStringFromObj). In this way, byte-oriented data can be read
from a channel, manipulated by calling Tcl_GetByteArrayFromObj and
related functions, and then written to a channel without the expense of ever
converting to or from UTF-8.
Tcl_Read is similar to Tcl_ReadChars, except that it doesn't 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 channel and stores them in
readBuf, performing end-of-line translations on the way. The return value
of Tcl_Read is the number of bytes, up to bytesToRead, written in
readBuf. The buffer produced by Tcl_Read is not null-terminated.
Its contents are valid from the zeroth position up to and excluding the
position indicated by the return value.
Tcl_ReadRaw is the same as Tcl_Read but does not
compensate for stacking. While Tcl_Read (and the other functions
in the API) always get their data from the topmost channel in the
stack the supplied channel is part of, Tcl_ReadRaw does
not. Thus this function is only 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.
Tcl_GetsObj consumes bytes from channel, 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 binary, 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 lineObjPtr's string representation. The end-of-line
character(s) are read and discarded.
If a line was successfully read, the return value is greater than or equal
to zero and indicates the number of bytes stored in lineObjPtr. If an
error occurs, Tcl_GetsObj returns -1 and records a POSIX error code
that can be retrieved with Tcl_GetErrno. Tcl_GetsObj also
returns -1 if the end of the file is reached; the Tcl_Eof procedure
can be used to distinguish an error from an end-of-file condition.
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 Tcl_InputBlocked
procedure may be invoked to determine if the channel is blocked because
of input unavailability.
Tcl_Gets is the same as Tcl_GetsObj except the resulting
characters are appended to the dynamic string given by
lineRead rather than a Tcl object.
Tcl_Ungets is used to add data to the input queue of a channel,
at either the head or tail of the queue. The pointer input points
to the data that is to be added. The length of the input to add is given
by inputLen. A non-zero value of addAtEnd 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 channel has a "sticky" EOF set, no data will be
added to the input queue. Tcl_Ungets returns inputLen or
-1 if an error occurs.
Tcl_WriteChars accepts bytesToWrite bytes of character data at
charBuf. The UTF-8 characters in the buffer are converted to the
channel's encoding and queued for output to channel. If
bytesToWrite is negative, Tcl_WriteChars expects charBuf
to be null-terminated and it outputs everything up to the null.
Data queued for output may not appear on the output device immediately, due
to internal buffering. If the data should appear immediately, call
Tcl_Flush after the call to Tcl_WriteChars, or set the
-buffering option on the channel to none. If you wish the data
to appear as soon as a complete line is accepted for output, set the
-buffering option on the channel to line mode.
The return value of Tcl_WriteChars 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, Tcl_WriteChars records a POSIX error code that may be
retrieved with Tcl_GetErrno.
Newline characters in the output data are translated to platform-specific
end-of-line sequences according to the -translation option for the
channel. This is done even if the channel has no encoding.
Tcl_WriteObj is similar to Tcl_WriteChars except it
accepts a Tcl object whose contents will be output to the channel. The
UTF-8 characters in writeObjPtr's string representation are converted
to the channel's encoding and queued for output to channel.
As a performance optimization, when writing to a channel with the encoding
binary, UTF-8 characters are not converted as they are written.
Instead, the bytes in writeObjPtr's internal representation as a
byte-array object are written to the channel. The byte-array representation
of the object will be constructed if it is needed. In this way,
byte-oriented data can be read from a channel, manipulated by calling
Tcl_GetByteArrayFromObj and related functions, and then written to a
channel without the expense of ever converting to or from UTF-8.
Tcl_Write is similar to Tcl_WriteChars except that it doesn't do
encoding conversions, regardless of the channel's encoding. It is
deprecated and exists for backwards compatibility with non-internationalized
Tcl extensions. It accepts bytesToWrite bytes of data at
byteBuf and queues them for output to channel. If
bytesToWrite is negative, Tcl_Write expects byteBuf to be
null-terminated and it outputs everything up to the null.
Tcl_WriteRaw is the same as Tcl_Write but does not
compensate for stacking. While Tcl_Write (and the other
functions in the API) always feed their input to the topmost channel
in the stack the supplied channel is part of, Tcl_WriteRaw does
not. Thus this function is only 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.
Tcl_Flush causes all of the buffered output data for channel
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.
The return value is normally TCL_OK.
If an error occurs, Tcl_Flush returns TCL_ERROR and
records a POSIX error code that can be retrieved with Tcl_GetErrno.
Tcl_Seek moves the access point in channel 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.
Tcl_Seek normally returns the new access point.
If an error occurs, Tcl_Seek returns -1 and records a POSIX error
code that can be retrieved with Tcl_GetErrno.
After an error, the access point may or may not have been moved.
Tcl_Tell returns the current access point for a channel. The returned
value is -1 if the channel does not support seeking.
Tcl_GetChannelOption retrieves, in optionValue, the value of one of
the options currently in effect for a channel, or a list of all options and
their values. The channel argument identifies the channel for which
to query an option or retrieve all options and their values.
If optionName 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 optionValue. If
optionName is NULL, the function stores an alternating list of option
names and their values in optionValue, using a series of calls to
Tcl_DStringAppendElement. The various preexisting options and
their possible values are described in the manual entry for the Tcl
fconfigure 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 socket command.
The procedure normally returns TCL_OK. If an error occurs, it returns
TCL_ERROR and calls Tcl_SetErrno to store an appropriate POSIX
error code.
Tcl_SetChannelOption sets a new value newValue
for an option optionName on channel.
The procedure normally returns TCL_OK. If an error occurs,
it returns TCL_ERROR; in addition, if interp is non-NULL,
Tcl_SetChannelOption leaves an error message in the interpreter's result.
Tcl_Eof returns a nonzero value if channel encountered
an end of file during the last input operation.
Tcl_InputBlocked returns a nonzero value if channel 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.
Tcl_InputBuffered 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.
Tcl_OutputBuffered 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.
The handles returned from Tcl_GetChannelHandle depend on the
platform and the channel type. On Unix platforms, the handle is
always a Unix file descriptor as returned from the open system
call. On Windows platforms, the handle is a file HANDLE when
the channel was created with Tcl_OpenFileChannel,
Tcl_OpenCommandChannel, or Tcl_MakeFileChannel. Other
channel types may return a different type of handle on Windows
platforms.
DString, fconfigure, filename, fopen, Tcl_CreateChannel
access point, blocking, buffered I/O, channel, channel driver, end of file, flush, input, nonblocking, output, read, seek, write
Copyright © 1996-1997 Sun Microsystems, Inc.
Copyright © 1995-1997 Roger E. Critchlow Jr.