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Read an input file- process it line by line
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Hi I'm trying to figure out how to process an input file, where you check to see if each line is a word. But I don't have any clue on how to begin doing so. I would use something like "load" I think? Then I would save that word in a variable.
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- 29 questions asked
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%at this point, insert the code to initialize the variable you will be storing the words in
%then
fid = fopen('YourFile.txt','rt');
while true
thisline = fgetl(fid);
if ~ischar(thisline); break; end %end of file
%now check whether the string in thisline is a "word", and store it if it is.
%then end fclose(fid);
%you have now loaded all of the data.
3 Comments
Thank you for your help. I'm a little confused why the "while true" part is there? Is true satisfied by "fopen" being valid?
Also I'm going to be putting this into a function.
It seems that the while loop ends when the line processer (fget1) encounters a non-word with the break. I'm hoping that this function continues to search through the rest of the file, checking if they are valid words, then entering them into a cell. Will this occur? (Can you also elaborate on how to make a cell that can be used throughout a function, not just within this subfunction? Global cell I think?)
Sorry for the long question!!
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why not to use while ~feof(fid)?!
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"while true" is an infinite loop. The loop will be exited by the "break" statement in the "if" inside the loop.
fgetl() returns a string ("string" is defined as an array of type char) *except* when fgetl() encounters end of file. The test is thus to see whether end of file has been it. It is not a test for a "non-word". You have not defined what a "word" or "non-word" is, so you will have to put that in at the point I show the comment.
feof(fid) only ever becomes true when there is no input remaining _and_ a read operation then attempts to read input that is not there. feof() does not look forward to see whether there is more input or not: it just reports on whether the eof flag has been set already by a read operation on an empty buffer having tried and failed to get input. If you had the case where, for example, you had a file that ended in XYZPDQ with no end-of-line indicator, then when a read operation got to that line, it would read the data that is there but *not* set the end-of-line indicator (in this case the buffer was not empty), and feof would not report true until the *next* read attempt found the buffer empty and nothing more to fetch.
This is how the C language standards and POSIX *define* end of file processing.
Because of this, you must test the result of each read operation, to see whether that was the read operation that found end-of-file.
If feof(fid) is true then reading from fid would fail, but feof() is not predictive, so the fact that feof() is false does not mean that a read will succeed.
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