puts

puts(3tcl)                    Tcl Built-In Commands                   puts(3tcl)



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NAME
       puts - Write to a channel

SYNOPSIS
       puts ?-nonewline? ?channelId? string
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DESCRIPTION
       Writes the characters given by string to the channel given by channelId.

       ChannelId must be an identifier for an open channel such as a Tcl
       standard 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
       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.  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 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 (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(3tcl), fileevent(3tcl), Tcl_StandardChannels(3tcl)

KEYWORDS
       channel, newline, output, write



Tcl                                    7.5                            puts(3tcl)