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markom |
'\"
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'\" Copyright (c) 1993 The Regents of the University of California.
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'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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'\" RCS: @(#) $Id: puts.n,v 1.1.1.1 2002-01-16 10:25:25 markom Exp $
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'\"
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.so man.macros
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.TH puts n 7.5 Tcl "Tcl Built-In Commands"
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.BS
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'\" Note: do not modify the .SH NAME line immediately below!
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.SH NAME
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puts \- Write to a channel
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.SH SYNOPSIS
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\fBputs \fR?\fB\-nonewline\fR? ?\fIchannelId\fR? \fIstring\fR
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.BE
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.SH DESCRIPTION
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.PP
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Writes the characters given by \fIstring\fR to the channel given
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by \fIchannelId\fR.
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\fIChannelId\fR must be a channel identifier such as returned from a
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previous invocation of \fBopen\fR or \fBsocket\fR. It must have been opened
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for output. If no \fIchannelId\fR is specified then it defaults to
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\fBstdout\fR. \fBPuts\fR normally outputs a newline character after
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\fIstring\fR, but this feature may be suppressed by specifying the
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\fB\-nonewline\fR switch.
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.PP
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Newline characters in the output are translated by \fBputs\fR to
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platform-specific end-of-line sequences according to the current
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value of the \fB\-translation\fR option for the channel (for example,
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on PCs newlines are normally replaced with carriage-return-linefeed
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sequences; on Macintoshes newlines are normally replaced with
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carriage-returns).
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See the \fBfconfigure\fR manual entry for a discussion of end-of-line
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translations.
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.PP
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Tcl buffers output internally, so characters written with \fBputs\fR
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may not appear immediately on the output file or device; Tcl will
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normally delay output until the buffer is full or the channel is
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closed.
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You can force output to appear immediately with the \fBflush\fR
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command.
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.PP
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When the output buffer fills up, the \fBputs\fR command will normally
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block until all the buffered data has been accepted for output by the
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operating system.
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If \fIchannelId\fR is in nonblocking mode then the \fBputs\fR command
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will not block even if the operating system cannot accept the data.
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Instead, Tcl continues to buffer the data and writes it in the
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background as fast as the underlying file or device can accept it.
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The application must use the Tcl event loop for nonblocking output
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to work; otherwise Tcl never finds out that the file or device is
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ready for more output data.
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It is possible for an arbitrarily large amount of data to be
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buffered for a channel in nonblocking mode, which could consume a
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large amount of memory.
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To avoid wasting memory, nonblocking I/O should normally
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be used in an event-driven fashion with the \fBfileevent\fR command
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(don't invoke \fBputs\fR unless you have recently been notified
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via a file event that the channel is ready for more output data).
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.SH "SEE ALSO"
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fileevent(n)
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.SH KEYWORDS
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channel, newline, output, write
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