Obviously one could loop through a file using fgetl or similar function and increment a counter, but is there a way to determine the number of lines in a file without doing such a loop?
I like to use the following code for exactly this task
fid = fopen('someTextFile.txt', 'rb');
%# Get file size.
fseek(fid, 0, 'eof');
fileSize = ftell(fid);
frewind(fid);
%# Read the whole file.
data = fread(fid, fileSize, 'uint8');
%# Count number of line-feeds and increase by one.
numLines = sum(data == 10) + 1;
fclose(fid);
It is pretty fast if you have enough memory to read the whole file at once. It should work for both Windows- and Linux-style line endings.
Edit: I measured the performance of the answers provided so far. Here is the result for determining the number of lines of a text file containing 1 million double values (one value per line). Average of 10 tries.
Author Mean time +- standard deviation (s)
------------------------------------------------------
Rody Oldenhuis 0.3189 +- 0.0314
Edric (2) 0.3282 +- 0.0248
Mehrwolf 0.4075 +- 0.0178
Jonas 1.0813 +- 0.0665
Edric (1) 26.8825 +- 0.6790
So fastest are the approaches using Perl and reading all the file as binary data. I would not be surprised, if Perl internally also read large blocks of the file at once instead of looping through it line by line (just a guess, do not know anything about Perl).
Using a simple fgetl()-loop is by a factor of 25-75 slower than the other approaches.
Edit 2: Included Edric's 2nd approach, which is much faster and on-par with the Perl solution, I'd say.