explanation for script containing while loop

I was given a script for reading data from a specific file, and although the script works, I don't understand one section of it, it reads as follows:

fid = fopen(Folder);% open file to read
fseek(fid,0,-1);% set read position to beginning of file, 
Linechk = strcmp(fgetl(fid),'*END*');% read in line 1
while Linechk == 0
    Linechk = strcmp(fgetl(fid),'*END*');% go through lines until '*END*' 
end

The main aim here is to find the line where the string END appears, following the appearance of END the data is stored. The question I have is that Linechk is equal to 0 initially (i.e. before the loop), then in following the loop it is equal to 1. I can't understand why it returns 1, surely the while loop only repeats when Linechk is equal to 0 therefore how does the condition remain true when it equals 1?

Entire code:

fid = fopen(Folder);% open file to read
fseek(fid,0,-1);% set read position to beginning of file, 
                % fseek(fileID, offset, origin).
Linechk = strcmp(fgetl(fid),'*END*');% read in line 1
while Linechk == 0
    Linechk = strcmp(fgetl(fid),'*END*');% go through lines until '*END*' 
end
n = 1;     
while 1;
    tline = fgetl(fid);% read in line
    if ~ischar(tline), break, end;% if end of file, break and finish
    data(n,:) = sscanf(tline,'%f');% put numbers in a matrix (in columns)
    n = n+1;
end
fclose(fid);% close file

Answer 1

[Wayne King]

I'm not sure I understand your question. Presumably, the first fgetl() call does not obtain the string END, so the string compare is 0. Then the while loop continues the string comparison until the string is END at which time the value of Linechk goes to 1.

Once you exit the loop the value of Linechk is 1. Or perhaps better stated, Linechk equal to 1 keeps the while loop from being evaluated.

[Richard]

So does fgetl continue until END is found? I guess I cant understand how fgetl looks at each individual line of the file without specifying the number of lines that the file has. For example, if I knew the file had 10 lines I thought I would have to loop through each individual line to find the line that contained END? The entire code has been added.

[Walter Roberson]

fgetl() reads one line of the file. strcmp() compares that one line to '*END*'. If the comparison fails then that line was not '*END*' and the loop needs to be repeated, reading one more line, testing it, etc.. When the comparison works then you are at the '*END*' line.

[Richard]

If I've understood this correctly, does that mean that following the while loop containing Linechk, the script will only be implemented for the remaining lines? For example, if Linechk is at line 9, then following this loop the script will perform some operation for line 10 and so on?

[Walter Roberson]

In such a situation, the fgetl() after that would fetch line 10, the one after that would fetch line 11, and so on.