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man pages section 1: User Commands

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Updated: Wednesday, February 9, 2022

gets (1t)


gets - Read a line from a channel


gets channelId ?varName?


gets(1t)                     Tcl Built-In Commands                    gets(1t)


       gets - Read a line from a channel

       gets channelId ?varName?

       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  com-
       mand.   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  charac-
       ters 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  chan-
       nelId  is  in  non-blocking  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 var-
       Name because of end-of-file or because of  insufficient  data  in  non-
       blocking  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.

       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 attributes(7) for descriptions of the following attributes:

       |Availability   | runtime/tcl-8    |
       |Stability      | Uncommitted      |

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

       blocking, channel, end of file, end of line, line, non-blocking, read

       Source code for open source software components in Oracle  Solaris  can
       be found at https://www.oracle.com/downloads/opensource/solaris-source-

       This    software    was    built    from    source     available     at
       https://github.com/oracle/solaris-userland.    The  original  community
       source was downloaded from  http://prdownloads.sourceforge.net/tcl/tcl-

       Further information about this software can be found on the open source
       community website at https://www.tcl.tk/.

Tcl                                   7.5                             gets(1t)