99 lines
3.4 KiB
Plaintext
99 lines
3.4 KiB
Plaintext
|
'\"
|
||
|
|
'\" 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.
|
||
|
|
'\"
|
||
|
|
.TH puts n 7.5 Tcl "Tcl Built-In Commands"
|
||
|
|
.so man.macros
|
||
|
|
.BS
|
||
|
|
'\" Note: do not modify the .SH NAME line immediately below!
|
||
|
|
.SH NAME
|
||
|
|
puts \- Write to a channel
|
||
|
|
.SH SYNOPSIS
|
||
|
|
\fBputs \fR?\fB\-nonewline\fR? ?\fIchannelId\fR? \fIstring\fR
|
||
|
|
.BE
|
||
|
|
.SH DESCRIPTION
|
||
|
|
.PP
|
||
|
|
Writes the characters given by \fIstring\fR to the channel given
|
||
|
|
by \fIchannelId\fR.
|
||
|
|
.PP
|
||
|
|
\fIChannelId\fR must be an identifier for an open channel such as a
|
||
|
|
Tcl standard channel (\fBstdout\fR or \fBstderr\fR), the return
|
||
|
|
value from an invocation of \fBopen\fR or \fBsocket\fR, or the result
|
||
|
|
of a channel creation command provided by a Tcl extension. The channel
|
||
|
|
must have been opened for output.
|
||
|
|
.PP
|
||
|
|
If no \fIchannelId\fR is specified then it defaults to
|
||
|
|
\fBstdout\fR. \fBPuts\fR normally outputs a newline character after
|
||
|
|
\fIstring\fR, but this feature may be suppressed by specifying the
|
||
|
|
\fB\-nonewline\fR switch.
|
||
|
|
.PP
|
||
|
|
Newline characters in the output are translated by \fBputs\fR to
|
||
|
|
platform-specific end-of-line sequences according to the current
|
||
|
|
value of the \fB\-translation\fR option for the channel (for example,
|
||
|
|
on PCs newlines are normally replaced with carriage-return-linefeed
|
||
|
|
sequences.
|
||
|
|
See the \fBfconfigure\fR manual entry for a discussion on ways in
|
||
|
|
which \fBfconfigure\fR will alter output.
|
||
|
|
.PP
|
||
|
|
Tcl buffers output internally, so characters written with \fBputs\fR
|
||
|
|
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 \fBflush\fR
|
||
|
|
command.
|
||
|
|
.PP
|
||
|
|
When the output buffer fills up, the \fBputs\fR command will normally
|
||
|
|
block until all the buffered data has been accepted for output by the
|
||
|
|
operating system.
|
||
|
|
If \fIchannelId\fR is in nonblocking mode then the \fBputs\fR 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 \fBfileevent\fR command
|
||
|
|
(do not invoke \fBputs\fR unless you have recently been notified
|
||
|
|
via a file event that the channel is ready for more output data).
|
||
|
|
.SH EXAMPLES
|
||
|
|
.PP
|
||
|
|
Write a short message to the console (or wherever \fBstdout\fR is
|
||
|
|
directed):
|
||
|
|
.PP
|
||
|
|
.CS
|
||
|
|
\fBputs\fR "Hello, World!"
|
||
|
|
.CE
|
||
|
|
.PP
|
||
|
|
Print a message in several parts:
|
||
|
|
.PP
|
||
|
|
.CS
|
||
|
|
\fBputs\fR -nonewline "Hello, "
|
||
|
|
\fBputs\fR "World!"
|
||
|
|
.CE
|
||
|
|
.PP
|
||
|
|
Print a message to the standard error channel:
|
||
|
|
.PP
|
||
|
|
.CS
|
||
|
|
\fBputs\fR stderr "Hello, World!"
|
||
|
|
.CE
|
||
|
|
.PP
|
||
|
|
Append a log message to a file:
|
||
|
|
.PP
|
||
|
|
.CS
|
||
|
|
set chan [open my.log a]
|
||
|
|
set timestamp [clock format [clock seconds]]
|
||
|
|
\fBputs\fR $chan "$timestamp - Hello, World!"
|
||
|
|
close $chan
|
||
|
|
.CE
|
||
|
|
.SH "SEE ALSO"
|
||
|
|
file(n), fileevent(n), Tcl_StandardChannels(3)
|
||
|
|
.SH KEYWORDS
|
||
|
|
channel, newline, output, write
|