Is it possible to parse file from end to beginning?

egor

 I can read and parse txt file from the beginning to the end this way:

Open "HOME:/Test.txt",file\Read;

Rewind file;

WHILE EOF=TRUE DO

Read_Str:=ReadStr(file);

ENDWHILE

But how to read the file in reverse order? Is it possible using "ReadStr" function?

soup

You could probably count the lines of the file with a FOR loop from beginning until EOF, then use ReadStr with \Line to start with the last line and FOR loop from the last line to the first line.

soup

Seemed to work -- as long as the line is not too long and can fit into a single string...

PROC exampleReadFileInReverse()

        VAR string text;
        VAR iodev infile;
        VAR num lineCounter:=0;
       
        Open "HOME:/test.txt",infile\Read;
       
        ! count number of lines in the file
        lineCounter:=0;
        WHILE text <> EOF DO
            IF text <> EOF THEN
                text := ReadStr(infile\Line:=lineCounter+1);
                IF text <> EOF lineCounter:=lineCounter+1;
            ENDIF
        ENDWHILE
       
        TPWrite "File has "+NumToStr(lineCounter,0)+" lines.";
       
        ! read file in reverse
        FOR i FROM lineCounter TO 1 STEP -1 DO
            text := ReadStr(infile\Line:=i);
            TPWrite "Line #"+NumToStr(i,0)+" = "+text;
            WaitTime 1;
        ENDFOR

    ENDPROC

egor

soup said:

Seemed to work -- as long as the line is not too long and can fit into a single string...

Thanks for answer! I will definitely try your code. I figured out how to solve the problem through a temporary array. It's working with any amount of strings in file.

soup

Looks good.

To clarify: I was stating that you'd have a problem if a single line is long, rather than a large quantity of lines -- make a test line with a hundred chars to see what I mean.