74 lines
3.0 KiB
Groff
74 lines
3.0 KiB
Groff
|
'\"
|
||
|
|
'\" Copyright (c) 1996 by Sun Microsystems, Inc.
|
||
|
|
'\"
|
||
|
|
'\" See the file "license.terms" for information on usage and redistribution
|
||
|
|
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||
|
|
'\"
|
||
|
|
'\" @(#) GetStdChan.3 1.2 96/03/08 13:59:57
|
||
|
|
'\"
|
||
|
|
.so man.macros
|
||
|
|
.TH Tcl_GetStdChannel 3 7.5 Tcl "Tcl Library Procedures"
|
||
|
|
.BS
|
||
|
|
'\" Note: do not modify the .SH NAME line immediately below!
|
||
|
|
.SH NAME
|
||
|
|
Tcl_GetStdChannel, Tcl_SetStdChannel \- procedures for retrieving and replacing the standard channels
|
||
|
|
.SH SYNOPSIS
|
||
|
|
.nf
|
||
|
|
\fB#include <tcl.h>\fR
|
||
|
|
.sp
|
||
|
|
Tcl_Channel
|
||
|
|
\fBTcl_GetStdChannel\fR(\fItype\fR)
|
||
|
|
.sp
|
||
|
|
\fBTcl_SetStdChannel\fR(\fIchannel, type\fR)
|
||
|
|
.sp
|
||
|
|
.SH ARGUMENTS
|
||
|
|
.AS Tcl_Channel channel in
|
||
|
|
.AP int type in
|
||
|
|
The identifier for the standard channel to retrieve or modify. Must be one of
|
||
|
|
\fBTCL_STDIN\fR, \fBTCL_STDOUT\fR, or \fBTCL_STDERR\fR.
|
||
|
|
.AP Tcl_Channel channel in
|
||
|
|
The channel to use as the new value for the specified standard channel.
|
||
|
|
.BE
|
||
|
|
|
||
|
|
.SH DESCRIPTION
|
||
|
|
.PP
|
||
|
|
Tcl defines three special channels that are used by various I/O related
|
||
|
|
commands if no other channels are specified. The standard input channel
|
||
|
|
has a channel name of \fBstdin\fR and is used by \fBread\fR and \fBgets\fR.
|
||
|
|
The standard output channel is named \fBstdout\fR and is used by
|
||
|
|
\fBputs\fR. The standard error channel is named \fBstderr\fR and is used for
|
||
|
|
reporting errors. In addition, the standard channels are inherited by any
|
||
|
|
child processes created using \fBexec\fR or \fBopen\fR in the absence of any
|
||
|
|
other redirections.
|
||
|
|
.PP
|
||
|
|
The standard channels are actually aliases for other normal channels. The
|
||
|
|
current channel associated with a standard channel can be retrieved by calling
|
||
|
|
\fBTcl_GetStdChannel\fR with one of
|
||
|
|
\fBTCL_STDIN\fR, \fBTCL_STDOUT\fR, or \fBTCL_STDERR\fR as the \fItype\fR. The
|
||
|
|
return value will be a valid channel, or NULL.
|
||
|
|
.PP
|
||
|
|
A new channel can be set for the standard channel specified by \fItype\fR
|
||
|
|
by calling \fBTcl_SetStdChannel\fR with a new channel or NULL in the
|
||
|
|
\fIchannel\fR argument. If the specified channel is closed by a later call to
|
||
|
|
\fBTcl_Close\fR, then the corresponding standard channel will automatically be
|
||
|
|
set to NULL.
|
||
|
|
.PP
|
||
|
|
If \fBTcl_GetStdChannel\fR is called before \fBTcl_SetStdChannel\fR, Tcl will
|
||
|
|
construct a new channel to wrap the appropriate platform-specific standard
|
||
|
|
file handle. If \fBTcl_SetStdChannel\fR is called before
|
||
|
|
\fBTcl_GetStdChannel\fR, then the default channel will not be created.
|
||
|
|
.PP
|
||
|
|
If one of the standard channels is set to NULL, either by calling
|
||
|
|
\fBTcl_SetStdChannel\fR with a null \fIchannel\fR argument, or by calling
|
||
|
|
\fBTcl_Close\fR on the channel, then the next call to \fBTcl_CreateChannel\fR
|
||
|
|
will automatically set the standard channel with the newly created channel. If
|
||
|
|
more than one standard channel is NULL, then the standard channels will be
|
||
|
|
assigned starting with standard input, followed by standard output, with
|
||
|
|
standard error being last.
|
||
|
|
|
||
|
|
.SH "SEE ALSO"
|
||
|
|
Tcl_Close(3), Tcl_CreateChannel(3)
|
||
|
|
|
||
|
|
.SH KEYWORDS
|
||
|
|
standard channel, standard input, standard output, standard error
|