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OpenDarwin 7.2.1 - man page for read (opendarwin section n)

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read(n) 			      Tcl Built-In Commands				  read(n)

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NAME
       read - Read from a channel

SYNOPSIS
       read ?-nonewline? channelId

       read channelId numChars
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DESCRIPTION
       In  the first form, the read command reads all of the data from channelId up to the end of
       the file.  If the -nonewline switch is specified then the last character of  the  file  is
       discarded  if  it is a newline.	In the second form, the extra argument specifies how many
       characters to read.  Exactly that many characters will be read and returned, unless  there
       are  fewer  than  numChars left in the file; in this case all the remaining characters are
       returned.  If the channel is configured to use a multi-byte encoding, then the  number  of
       characters read may not be the same as the number of bytes read.

       ChannelId must be an identifier for an open channel such as the Tcl standard input channel |
       (stdin), 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 input.

       If  channelId  is  in  nonblocking  mode,  the  command may not read as many characters as
       requested: once all available input has been read, the command will return the  data  that
       is  available  rather than blocking for more input.  If the channel is configured to use a
       multi-byte encoding, then there may actually be some bytes remaining in the internal  buf-
       fers that do not form a complete character.  These bytes will not be returned until a com-
       plete character is available or end-of-file is reached.	The -nonewline switch is  ignored
       if the command returns before reaching the end of the file.

       Read  translates  end-of-line  sequences in the input into newline characters according to
       the -translation option for the channel.  See the fconfigure manual entry for a discussion
       on ways in which fconfigure will alter input.

USE WITH SERIAL PORTS
       For most applications a channel connected to a serial port should be configured to be non-
       blocking: fconfigure channelId -blocking 0.  Then read behaves much like described  above.
       Care must be taken when using read on blocking serial ports:

       read channelId numChars
	      In this form read blocks until numChars have been received from the serial port.

       read channelId
	      In  this	form  read  blocks  until the reception of the end-of-file character, see
	      fconfigure -eofchar. If there no end-of-file character has been configured for  the
	      channel, then read will block forever.

SEE ALSO
       file(n), eof(n), fblocked(n), fconfigure(n), Tcl_StandardChannels(3)

KEYWORDS
       blocking, channel, end of line, end of file, nonblocking, read, translation, encoding

Tcl					       8.1					  read(n)
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