bionic (3) gets.3tcl.gz

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