puts(n) Tcl Built-In Commands puts(n)_________________________________________________________________NAMEputs - Write to a channel
SYNOPSISputs ?-nonewline? ?channelId? string
_________________________________________________________________DESCRIPTION
Writes the characters given by string to the channel given
by channelId. ChannelId must be a channel identifier such
as returned from a previous invocation of open or socket.
It must have been opened for output. If no channelId is
specified then it defaults to stdout. Puts normally out-
puts a newline character after string, but this feature
may be suppressed by specifying the -nonewline switch.
Newline characters in the output are translated by puts to
platform-specific end-of-line sequences according to the
current value of the -translation option for the channel
(for example, on PCs newlines are normally replaced with
carriage-return-linefeed sequences; on Macintoshes new-
lines are normally replaced with carriage-returns). See
the fconfigure manual entry for a discussion of end-of-
line translations.
Tcl buffers output internally, so characters written with
puts 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 flush command.
When the output buffer fills up, the puts command will
normally block until all the buffered data has been
accepted for output by the operating system. If channelId
is in nonblocking mode then the puts 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 fileevent command (don't
invoke puts unless you have recently been notified via a
file event that the channel is ready for more output
data).
Tcl 7.5 1
puts(n) Tcl Built-In Commands puts(n)SEE ALSOfileevent(n)KEYWORDS
channel, newline, output, write
Tcl 7.5 2
