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Tcl Library Procedures Tcl_OpenFileChannel(3TCL)

_________________________________________________________________

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 facili-

ties using channels

SYNOPSIS

#include

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 Last change: 8.3 1

Tcl Library Procedures Tcl_OpenFileChannel(3TCL)

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)

Tcl Last change: 8.3 2

Tcl Library Procedures Tcl_OpenFileChannel(3TCL)

int

Tcl_SetChannelOption(interp, channel, optionName, newValue)

ARGUMENTS

Tcl_Interp *interp (in) Used for

error report-

ing and to look up a channel registered in it. CONST char *fileName (in) The name of a

local or net-

work 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 permis-

sions 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-

Tcl Last change: 8.3 3

Tcl Library Procedures Tcl_OpenFileChannel(3TCL)

switch argu-

ments to the

Tcl exec com-

mand. int flags (in) Specifies the disposition of the stdio handles in pipeline:

OR-ed combi-

nation 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 stan-

dard input of the invoking process; likewise for

TCL_STDOUT

and

TCL_STDERR.

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 redirec-

tions cause Tcl Last change: 8.3 4

Tcl Library Procedures Tcl_OpenFileChannel(3TCL)

an error. ClientData handle (in) Operating system

specific han-

dle for I/O to a file. For Unix this is a file descriptor, for Windows

it is a HAN-

DLE.

int readOrWrite (in) OR-ed combi-

nation of

TCL_READABLE

and

TCL_WRITABLE

to indicate

what opera-

tions are

valid on han-

dle. CONST char *channelName (in) The name of the channel. int *modePtr (out) Points at an

integer vari-

able that will receive

an OR-ed com-

bination 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

Tcl Last change: 8.3 5

Tcl Library Procedures Tcl_OpenFileChannel(3TCL)

for input or output. Must have been the return value

from a pro-

cedure 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, |

object. Oth- |

erwise, the | data will | replace the |

existing con- |

tents of the | object. | char *readBuf (out) || A buffer in | which to | store the | bytes read | Tcl Last change: 8.3 6

Tcl Library Procedures Tcl_OpenFileChannel(3TCL)

from the | channel. | int bytesToRead (in) || The number of | bytes to read | from the | channel. The |

buffer read- |

Buf must be | large enough | to hold this | many bytes. |

Tcl_Obj *lineObjPtr (in/out) ||

Tcl_DString *lineRead (in/out) ||

been initial- |

ized by the | caller. The | line read | will be | appended to | any data | already in | the dynamic | string. | CONST char *input (in) || The input to | Tcl Last change: 8.3 7

Tcl Library Procedures Tcl_OpenFileChannel(3TCL)

add to a | channel | buffer. | int inputLen (in) || Length of the | input | int addAtEnd (in) ||

Flag indicat- |

ing whether | the input | should be | added to the |

end or begin- |

ning of the | channel | buffer.

Tcl_Obj *writeObjPtr (in) A pointer to

a Tcl Object

whose con-

tents will be output to the channel.

CONST char *charBuf (in) A buffer con-

taining the characters to output to the channel.

CONST char *byteBuf (in) A buffer con-

taining the

bytes to out-

put to the channel. int bytesToWrite (in) The number of

bytes to con-

sume from charBuf or byteBuf and output to the channel.

Tcl_WideInt offset (in) How far to

move the access point

in the chan-

nel at which the next Tcl Last change: 8.3 8

Tcl Library Procedures Tcl_OpenFileChannel(3TCL)

input or out-

put 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 chan-

nel. 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 fconfig-

ure 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 initial-

ized by the caller. CONST char *newValue (in) New value for Tcl Last change: 8.3 9

Tcl Library Procedures Tcl_OpenFileChannel(3TCL)

the option given by optionName.

_________________________________________________________________

DESCRIPTION

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 dev-

ice types. The channel mechanism is extensible to new chan-

nel 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

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

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 Tcl Last change: 8.3 10

Tcl Library Procedures Tcl_OpenFileChannel(3TCL)

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 subpro-

cess can be read from the channel; otherwise it goes to this

application's standard output. If TCL_STDERR is set, stan-

dard 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

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

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 Last change: 8.3 11

Tcl Library Procedures Tcl_OpenFileChannel(3TCL)

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

Tcl_RegisterChannel adds a channel to the set of channels

accessible in interp. After this call, Tcl programs execut-

ing 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 exe-

cuting 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 initial-

ized 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

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 Tcl Last change: 8.3 12

Tcl Library Procedures Tcl_OpenFileChannel(3TCL)

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

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 chan-

nels (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

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

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 destroy-

ing 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 out-

put 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 back-

ground and the channel will be closed once all of the buf-

fered 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. Tcl Last change: 8.3 13

Tcl Library Procedures Tcl_OpenFileChannel(3TCL)

Note: it is not safe to call Tcl_Close on a channel that has

been registered using Tcl_RegisterChannel; see the documen-

tation 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 AND TCL_READ |

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 charac- |

ters, 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 con- |

dition. Use Tcl_Eof and Tcl_InputBlocked to tell which of |

these conditions actually occurred. |

Tcl_ReadChars translates the various end-of-line representa- |

tions into the canonical \n internal representation accord- |

ing 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 com- |

mand. | 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 con- |

structed if it is needed (e.g., because of a call to | Tcl Last change: 8.3 14

Tcl Library Procedures Tcl_OpenFileChannel(3TCL)

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 encod- |

ing. It is deprecated and exists for backwards compatibil- |

ity 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 chan- |

nel 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 AND TCL_GETS |

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 una- |

vailability. | Tcl Last change: 8.3 15

Tcl Library Procedures Tcl_OpenFileChannel(3TCL)

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 |

Tcl_Ungets is used to add data to the input queue of a chan- |

nel, 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, TCL_WRITEOBJ, AND TCL_WRITE |

Tcl_WriteChars accepts bytesToWrite bytes of character data |

at charBuf. The UTF-8 characters in the buffer are con- |

verted 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 every- |

thing 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 com- |

plete 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 indi- |

cate 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 out- |

put 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 | Tcl Last change: 8.3 16

Tcl Library Procedures Tcl_OpenFileChannel(3TCL)

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, manipu- |

lated by calling Tcl_GetByteArrayFromObj and related func- |

tions, 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 compa- |

tibility 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 out- |

puts everything up to the null. |

Tcl_WriteRaw is the same as Tcl_Write but does not compen- |

sate 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 transforma- |

tional 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

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 immedi-

ately if the channel is nonblocking; it starts a background

flush that will write the buffered data to the channel even-

tually, 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

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 Last change: 8.3 17

Tcl Library Procedures Tcl_OpenFileChannel(3TCL)

TCL_TELL

Tcl_Tell returns the current access point for a channel. The

returned value is -1 if the channel does not support seek-

ing.

TCL_GETCHANNELOPTION

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 option-

Value. If optionName is NULL, the function stores an alter-

nating 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 com-

mand. 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

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 addi-

tion, if interp is non-NULL, Tcl_SetChannelOption leaves an

error message in the interpreter's result.

TCL_EOF

Tcl_Eof returns a nonzero value if channel encountered an

end of file during the last input operation.

TCL_INPUTBLOCKED

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

Tcl Last change: 8.3 18

Tcl Library Procedures Tcl_OpenFileChannel(3TCL)

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

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. PLATFORM ISSUES

The handles returned from Tcl_GetChannelHandle depend on the

platform and the channel type. On Unix platforms, the han-

dle 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 dif-

ferent type of handle on Windows platforms. On the Macin-

tosh platform, the handle is a file reference number as returned from HOpenDF.

ATTRIBUTES

See attributes(5) for descriptions of the following attri-

butes:

_______________________________________

| ATTRIBUTE TYPE | ATTRIBUTE VALUE|

|____________________|__________________|_

| Availability | runtime/tcl-8 |

|____________________|__________________|_

| Interface Stability| Uncommitted |

|____________________|_________________|

NOTES Source for Tcl is available on http://opensolaris.org. Tcl Last change: 8.3 19

Manual Pages for UNIX Operating System command usage for man Tcl_OpenCommandChannel

NAME

Tcl_OpenFileChannel, Tcl_OpenCommandChannel,

SYNOPSIS

Tcl_OpenCommandChannel(interp, argc, argv, flags)

DESCRIPTION

Tcl_OpenCommandChannel provides a C-level interface to the

Tcl_OpenCommandChannel returns NULL and records a POSIX

addition, Tcl_OpenCommandChannel leaves an error message in

TCL_ERROR, and the error message is left in the

nels (stdout, stderr, stdin), and will return TCL_ERROR if

TCL_OK. If an error occurs, Tcl_Close returns TCL_ERROR and

Tcl_Flush returns TCL_ERROR and records a POSIX error code

an error occurs, it returns TCL_ERROR and calls Tcl_SetErrno

TCL_OK. If an error occurs, it returns TCL_ERROR; in addi-

TCL_INPUTBLOCKED

TCL_INPUTBUFFERED

TCL_OUTPUTBUFFERED

Tcl_OpenFileChannel, Tcl_OpenCommandChannel, or

SEE ALSO

ATTRIBUTES

| ATTRIBUTE TYPE | ATTRIBUTE VALUE|