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Tcl file READ command…

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  • March 12, 2009 at 8:01 pm #50709
    Tom Rioux
    Participant

      I’m on 5.6 AIX….

      I haven’t had to use this command very much and I can’t seem to find it documented anywhere, but here is what I’m looking for.   I have a new line file and I want to ignore the first few header lines in the file.  Is there a way that I can specify to start reading on a certain line?

      Thanks….

      Tom Rioux

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      • March 12, 2009 at 8:23 pm #67190
        Max Drown (Infor)
        Keymaster

          With tcl read I don’t think you can specify to read in a file from x to y. I think you can read a certain number of bites, but not specify where to start. Charlie will know if there’s a way to do this.

          When I’m working with files, I normally will slurp the entire file into a variable and then work with the file from there.

          An example:

          Code:

          set fileName [lindex $argv 0]
          # Usage: test.tcl file.txt

          set f [open $fileName r]
          fconfigure $f -translation binary
          set msg [read $f]
          close $f

          # You whole file is now in $msg

          foreach line [split $msg n] {
             # Skip blank lines
             # if {$line == “”} {continue}
          }

          I’m sure there are other ways, even “better” ways to this, but this has worked for me in the past.

          -- Max Drown (Infor)

        • March 12, 2009 at 8:37 pm #67191
          Jim Kosloskey
          Participant

            Tom,

            I opewn the file getting a file handle.

            Then I use a while loop checking for eof

                  while ![eof $filehandle]{

            Inside the while loop I use gets to get each line. I also check for eof and break inside the while (wearing suspenders and a belt is really safe 😆 ).

            You could then keep a counter and as long as the counter is less than what you want continue inside the while. Once you are at the lines you want, start processing.

            The read command won’t do what you want as reads in the entire file or just so many characters.

            email: jim.kosloskey@jim-kosloskey.com 29+ years Cloverleaf, 59 years IT - old fart.

          • March 12, 2009 at 8:41 pm #67192
            Max Drown (Infor)
            Keymaster

              Here’s an example from the web of what Jim is referring to:

              set f [open /home/keith/.profile]
              while {[gets $f line] >= 0} {
              [code]set f [open /home/keith/.profile]
              while {[gets $f line] >= 0} {

              -- Max Drown (Infor)

            • March 12, 2009 at 10:42 pm #67193
              Tom Rioux
              Participant

                Thanks guys for all your help.  The counter was the way to go.  Here is what got it to work for me:

                           set fd [open $msgdir/$filename r+]

                           set ctr 1

                           foreach line [split [read $fd] n] {

                             if [expr $ctr > 8] {

                               lappend contents $line

                             }

                             incr ctr

                           }

                           close $fd

                Tom

              • March 12, 2009 at 10:50 pm #67194
                Charlie Bursell
                Participant

                  The simplest method to read a file is:

                  set fd [open file]

                  while {[gets $fd rec] >= 0} {

                       process the record

                  }

                  close $fd

                  As for reading parts of a file refer to the seek and tell commands

                   

                  tell channelId  returns the current file offset

                  seek channelId offset ?origin?”   moves to a specific offset

                • March 13, 2009 at 12:17 pm #67195
                  Russ Ross
                  Participant

                    Another handy alerternative at the command line to say output starting at line 100 to the end of the file is to use the tail command at the UNIX prompt as follows:

                    tail +100 myFile

                    Russ Ross
                    RussRoss318@gmail.com

                  • March 13, 2009 at 12:18 pm #67196
                    Keith McLeod
                    Participant

                      Another command that I like when reading one line at a time is

                      for_file line {

                      do something with the line

                      }

                      Like other for loops you can throw in a counter if you wish….

                    • March 13, 2009 at 2:57 pm #67197
                      Max Drown (Infor)
                      Keymaster

                        Russ Ross wrote:

                        Another handy alerternative at the command line to say output starting at line 100 to the end of the file is to use the tail command at the UNIX prompt as follows:

                        tail +100 myFile

                        Good one!

                        in Tcl it would be something like set msg [exec tail +100 $fileName]

                        -- Max Drown (Infor)

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