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.                                                         |

     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  |
     buffers that do not form a complete character.  These  bytes  |
     will not be returned until a complete 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 new-
     line 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.

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

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

Tcl                     Last change: 8.1                        1