gets(3tcl)

NAME

   gets - Read a line from a channel

SYNOPSIS

   gets channelId ?varName?
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DESCRIPTION

   This  command reads the next line from channelId, returns everything in
   the line up to (but not including) the  end-of-line  character(s),  and
   discards the end-of-line character(s).

   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 varName is omitted the  line  is  returned  as  the  result  of  the
   command.   If  varName  is  specified  then  the  line is placed in the
   variable by that name and the return value is a count of the number  of
   characters returned.

   If  end  of  file occurs while scanning for an end of line, the command
   returns whatever input  is  available  up  to  the  end  of  file.   If
   channelId  is in nonblocking mode and there is not a full line of input
   available, the command returns an empty string and does not consume any
   input.   If  varName  is  specified  and an empty string is returned in
   varName because of end-of-file  or  because  of  insufficient  data  in
   nonblocking mode, then the return count is -1.  Note that if varName is
   not specified then the end-of-file and no-full-line-available cases can
   produce the same results as if there were an input line consisting only
   of the end-of-line character(s).  The eof and fblocked commands can  be
   used to distinguish these three cases.

EXAMPLE

   This example reads a file one line at a time and prints it out with the
   current line number attached to the start of each line.

          set chan [open "some.file.txt"]
          set lineNumber 0
          while {[gets $chan line] >= 0} {
              puts "[incr lineNumber]: $line"
          }
          close $chan

SEE ALSO

   file(3tcl), eof(3tcl), fblocked(3tcl), Tcl_StandardChannels(3tcl)

KEYWORDS

   blocking, channel, end of file, end of line, line, nonblocking, read

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