12.5.31    puts

Description:   Write to an IO channel ( Com. port, TCP socket, file or command pipe). Replaced by SETVAL for most applications


Syntax:         puts ?-nonewline? ?channelId? string


Argument:     option, IO channel



See Also:       SETVAL, file, filevent,


Examples:      #  example 1
# Sends a line of text to the server socket

# Arguments:

# s                           Open socket to server.

# line                       Line of text to be sent to the server.

# Results:

# Closes socket $s and un-sets variables.

proc send_line {s  line} {

                                puts $s $line

                                 flush $s



# Example 2

# Report1 is a Text File used for report data

     set fileid [open "../ReportClient2.txt" a+]

     seek $fileid 0 start

     puts $fileid "----- Water Use Report-------\nPage 1"

 # Insert data into table


     close $fileid

SETVAL recommended interface for most WebAccess Scripts.  SETVAL can change the value of a specific tag in an established communications driver.

The puts  command is maintained to support imported Tcl scripts to customize WebAccess (for example sending email).  The user must define and open an IO channel.  There is no standard IO (stdout) in WebAccess. For most users, IT IS NOT RECOMMENDED TO USE puts.


The puts command 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.

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).

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).