Provided by: tcl8.6-doc_8.6.10+dfsg-1_all bug


       puts - Write to a channel


       puts ?-nonewline? ?channelId? string


       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

       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

       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).


       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


       file(3tcl), fileevent(3tcl), Tcl_StandardChannels(3tcl)


       channel, newline, output, write