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1 | '\" |
2 | '\" Copyright (c) 1996 by Sun Microsystems, Inc. | |
3 | '\" | |
4 | '\" See the file "license.terms" for information on usage and redistribution | |
5 | '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. | |
6 | '\" | |
7 | '\" RCS: @(#) $Id: GetStdChan.3,v 1.4 2001/12/10 15:50:46 dgp Exp $ | |
8 | '\" | |
9 | '\" The definitions below are for supplemental macros used in Tcl/Tk | |
10 | '\" manual entries. | |
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70 | '\" RCS: @(#) $Id: man.macros,v 1.4 2000/08/25 06:18:32 ericm Exp $ | |
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72 | '\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages. | |
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205 | '\" # SO - start of list of standard options | |
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207 | .SH "STANDARD OPTIONS" | |
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218 | See the \\fBoptions\\fR manual entry for details on the standard options. | |
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220 | '\" # OP - start of full description for a single option | |
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225 | Command-Line Name: \\fB\\$1\\fR | |
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243 | \\$1\l'|0\(ul'\\$2 | |
244 | .. | |
245 | .TH Tcl_GetStdChannel 3 7.5 Tcl "Tcl Library Procedures" | |
246 | .BS | |
247 | '\" Note: do not modify the .SH NAME line immediately below! | |
248 | .SH NAME | |
249 | Tcl_GetStdChannel, Tcl_SetStdChannel \- procedures for retrieving and replacing the standard channels | |
250 | .SH SYNOPSIS | |
251 | .nf | |
252 | \fB#include <tcl.h>\fR | |
253 | .sp | |
254 | Tcl_Channel | |
255 | \fBTcl_GetStdChannel\fR(\fItype\fR) | |
256 | .sp | |
257 | \fBTcl_SetStdChannel\fR(\fIchannel, type\fR) | |
258 | .sp | |
259 | .SH ARGUMENTS | |
260 | .AS Tcl_Channel channel in | |
261 | .AP int type in | |
262 | The identifier for the standard channel to retrieve or modify. Must be one of | |
263 | \fBTCL_STDIN\fR, \fBTCL_STDOUT\fR, or \fBTCL_STDERR\fR. | |
264 | .AP Tcl_Channel channel in | |
265 | The channel to use as the new value for the specified standard channel. | |
266 | .BE | |
267 | ||
268 | .SH DESCRIPTION | |
269 | .PP | |
270 | Tcl defines three special channels that are used by various I/O related | |
271 | commands if no other channels are specified. The standard input channel | |
272 | has a channel name of \fBstdin\fR and is used by \fBread\fR and \fBgets\fR. | |
273 | The standard output channel is named \fBstdout\fR and is used by | |
274 | \fBputs\fR. The standard error channel is named \fBstderr\fR and is used for | |
275 | reporting errors. In addition, the standard channels are inherited by any | |
276 | child processes created using \fBexec\fR or \fBopen\fR in the absence of any | |
277 | other redirections. | |
278 | .PP | |
279 | The standard channels are actually aliases for other normal channels. The | |
280 | current channel associated with a standard channel can be retrieved by calling | |
281 | \fBTcl_GetStdChannel\fR with one of | |
282 | \fBTCL_STDIN\fR, \fBTCL_STDOUT\fR, or \fBTCL_STDERR\fR as the \fItype\fR. The | |
283 | return value will be a valid channel, or NULL. | |
284 | .PP | |
285 | A new channel can be set for the standard channel specified by \fItype\fR | |
286 | by calling \fBTcl_SetStdChannel\fR with a new channel or NULL in the | |
287 | \fIchannel\fR argument. If the specified channel is closed by a later call to | |
288 | \fBTcl_Close\fR, then the corresponding standard channel will automatically be | |
289 | set to NULL. | |
290 | .PP | |
291 | If \fBTcl_GetStdChannel\fR is called before \fBTcl_SetStdChannel\fR, Tcl will | |
292 | construct a new channel to wrap the appropriate platform-specific standard | |
293 | file handle. If \fBTcl_SetStdChannel\fR is called before | |
294 | \fBTcl_GetStdChannel\fR, then the default channel will not be created. | |
295 | .PP | |
296 | If one of the standard channels is set to NULL, either by calling | |
297 | \fBTcl_SetStdChannel\fR with a NULL \fIchannel\fR argument, or by calling | |
298 | \fBTcl_Close\fR on the channel, then the next call to \fBTcl_CreateChannel\fR | |
299 | will automatically set the standard channel with the newly created channel. If | |
300 | more than one standard channel is NULL, then the standard channels will be | |
301 | assigned starting with standard input, followed by standard output, with | |
302 | standard error being last. | |
303 | .PP | |
304 | See \fBTcl_StandardChannels\fR for a general treatise about standard | |
305 | channels and the behaviour of the Tcl library with regard to them. | |
306 | .PP | |
307 | ||
308 | .SH "SEE ALSO" | |
309 | Tcl_Close(3), Tcl_CreateChannel(3), Tcl_Main(3), tclsh(1) | |
310 | ||
311 | .SH KEYWORDS | |
312 | standard channel, standard input, standard output, standard error |