fgetl - still a valid function?

I am trying to adapt someonelse's old (~2010) code for my use (run monte carlo of another program) . The old code uses the function "fgetl"

%READ HYDRUS OUTPUT FILES - This block reads for all the realizations of
%the Nod_inf.out file and stores the water content profiles for t=10 days in Prof_out table.
prof_out=zeros(101,num_sim+1);
for i=1:num_sim
    fileID_out=fopen(strcat(path{i},'\nod_inf.out'));
    skip_lines=123;
    for k=1:(skip_lines)
        x=fgetl(fileID_out);
    end
    temp=fscanf(fileID_out,'%f',[11,101])';
    prof_out(:,i+1)=temp(:,4);
    fclose(fileID_out);
end
prof_out(:,1)=temp(:,2);

But I keep getting the following error:

Error in fgetl (line 32)
[tline,lt] = fgets(fid);

Error in PAFBHydrusMC (line 144)
        x=fgetl(fileID_out);
 

Why? I have double checked that it is writen with a lower case "L" and not the number 1... Thanks for any direction on this!

Answer 1

[Voss]

Yes, fgetl is still a valid built-in MATLAB function.

(Notice, the error message says, "error in fgetl (line 32)", so you know MATLAB is finding fgetl and getting to line 32 of it. If fgetl was no longer a valid function, you'd get an error message along the lines of "Unrecognized function or variable fgetl ...")

We'd have to see the rest of the error message to know for sure what the problem is, but it's most likely:

"Invalid file identifier.  Use fopen to generate a valid file identifier."

If that is the case, it means that the file

strcat(path{i},'\nod_inf.out')

could not be opened for reading. Does the file exist?

Generally, every time you (or the person who wrote this code) use fopen, you should check that the file was successfully opened, and if not (in which case the file ID is -1) take an appropriate action (e.g., throw an error - fopen returns a message as its second output for you for this purpose - or just return from the function). For instance:

prof_out=zeros(101,num_sim+1);

for i=1:num_sim
    
    file_name = strcat(path{i},'\nod_inf.out');
    [fileID_out,err_msg] = fopen(file_name);
    if fileID_out == -1
        error('Could not open %s: %s',file_name,err_msg);
    end
    
    skip_lines=123;
    for k=1:(skip_lines)
        x=fgetl(fileID_out);
    end
    temp=fscanf(fileID_out,'%f',[11,101])';
    prof_out(:,i+1)=temp(:,4);
    fclose(fileID_out);
    
end

prof_out(:,1)=temp(:,2);

This prevents subsequent errors in fgetl or whatever file reading/writing function(s) are used, and lets you know the root cause of the problem right away.

[Wesser]

I'll give this a whirl. Thanks!

[Voss]

You're welcome!