Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help
puts(n)			     Tcl Built-In Commands		       puts(n)

______________________________________________________________________________

NAME
       puts - Write to a channel

SYNOPSIS
       puts ?-nonewline? ?channelId? string
______________________________________________________________________________

DESCRIPTION
       Writes  the  characters	given  by string to the	channel	given by chan-
       nelId.

       ChannelId must be an identifier for an open channel such	as a Tcl stan-
       dard channel (stdout or stderr),	the return value from an invocation of
       open or socket, or the result of	a channel creation command provided by
       a Tcl extension.	The channel must have been opened for output.

       If  no channelId	is specified then it defaults to stdout. Puts normally
       outputs a newline character after string, but this feature may be  sup-
       pressed 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.   See  the
       fconfigure  manual  entry  for a	discussion on ways in which fconfigure
       will alter output.

       Tcl buffers output internally, so characters written with puts may  not
       appear immediately on the output	file or	device;	 Tcl will normally de-
       lay 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 operat-
       ing  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 back-
       ground as fast as the underlying	file or	device can accept it.  The ap-
       plication  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	(do not	invoke puts unless you have recently been notified via
       a file event that the channel is	ready for more output data).

EXAMPLES
       Write a short message to	the console (or	wherever stdout	is directed):

	      puts "Hello, World!"

       Print a message in several parts:

	      puts -nonewline "Hello, "
	      puts "World!"

       Print a message to the standard error channel:

	      puts stderr "Hello, World!"

       Append a	log message to a file:

	      set chan [open my.log a]
	      set timestamp [clock format [clock seconds]]
	      puts $chan "$timestamp - Hello, World!"
	      close $chan

SEE ALSO
       file(n),	fileevent(n), Tcl_StandardChannels(3)

KEYWORDS
       channel,	newline, output, write

Tcl				      7.5			       puts(n)

NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | SEE ALSO | KEYWORDS

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=puts.tcl86&manpath=FreeBSD+13.0-RELEASE+and+Ports>

home | help