puts.n
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- '"
- '" Copyright (c) 1993 The Regents of the University of California.
- '" Copyright (c) 1994-1996 Sun Microsystems, Inc.
- '"
- '" See the file "license.terms" for information on usage and redistribution
- '" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
- '"
- '" RCS: @(#) $Id: puts.n,v 1.5.8.1 2004/10/27 14:23:57 dkf Exp $
- '"
- .so man.macros
- .TH puts n 7.5 Tcl "Tcl Built-In Commands"
- .BS
- '" Note: do not modify the .SH NAME line immediately below!
- .SH NAME
- puts - Write to a channel
- .SH SYNOPSIS
- fBputs fR?fB-nonewlinefR? ?fIchannelIdfR? fIstringfR
- .BE
- .SH DESCRIPTION
- .PP
- Writes the characters given by fIstringfR to the channel given
- by fIchannelIdfR.
- .PP
- .VS
- fIChannelIdfR must be an identifier for an open channel such as a
- Tcl standard channel (fBstdoutfR or fBstderrfR), the return
- value from an invocation of fBopenfR or fBsocketfR, or the result
- of a channel creation command provided by a Tcl extension. The channel
- must have been opened for output.
- .VE
- .PP
- If no fIchannelIdfR is specified then it defaults to
- fBstdoutfR. fBPutsfR normally outputs a newline character after
- fIstringfR, but this feature may be suppressed by specifying the
- fB-nonewlinefR switch.
- .PP
- Newline characters in the output are translated by fBputsfR to
- platform-specific end-of-line sequences according to the current
- value of the fB-translationfR option for the channel (for example,
- on PCs newlines are normally replaced with carriage-return-linefeed
- sequences; on Macintoshes newlines are normally replaced with
- carriage-returns).
- See the fBfconfigurefR manual entry for a discussion on ways in
- which fBfconfigurefR will alter output.
- .PP
- Tcl buffers output internally, so characters written with fBputsfR
- may not appear immediately on the output file or device; Tcl will
- normally delay output until the buffer is full or the channel is
- closed.
- You can force output to appear immediately with the fBflushfR
- command.
- .PP
- When the output buffer fills up, the fBputsfR command will normally
- block until all the buffered data has been accepted for output by the
- operating system.
- If fIchannelIdfR is in nonblocking mode then the fBputsfR command
- will not block even if the operating system cannot accept the data.
- Instead, Tcl continues to buffer the data and writes it in the
- background as fast as the underlying file or device can accept it.
- The application must use the Tcl event loop for nonblocking output
- to work; otherwise Tcl never finds out that the file or device is
- ready for more output data.
- It is possible for an arbitrarily large amount of data to be
- buffered for a channel in nonblocking mode, which could consume a
- large amount of memory.
- To avoid wasting memory, nonblocking I/O should normally
- be used in an event-driven fashion with the fBfileeventfR command
- (don't invoke fBputsfR unless you have recently been notified
- via a file event that the channel is ready for more output data).
- .SH EXAMPLES
- Write a short message to the console (or wherever fBstdoutfR is
- directed):
- .CS
- fBputsfR "Hello, World!"
- .CE
- .PP
- Print a message in several parts:
- .CS
- fBputsfR -nonewline "Hello, "
- fBputsfR "World!"
- .CE
- .PP
- Print a message to the standard error channel:
- .CS
- fBputsfR stderr "Hello, World!"
- .CE
- .PP
- Append a log message to a file:
- .CS
- set chan [open my.log a]
- set timestamp [clock format [clock seconds]]
- fBputsfR $chan "$timestamp - Hello, World!"
- close $chan
- .CE
- .SH "SEE ALSO"
- file(n), fileevent(n), Tcl_StandardChannels(3)
- .SH KEYWORDS
- channel, newline, output, write