Kirill
Posts:
139
Registered:
3/28/06
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Re: Number of line in a text file
Posted:
Nov 2, 2006 11:48 AM
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To illustrate this idea the following code creates ~100M text file and
counts lines by fgetl() and by reading in the big chunks (~1M). You
can see that in the first case you need 457 seconds and in the second
about 7 seconds - 65 times more!
Kirill
clc
% write N lines
fname = 'test.txt';
N = 1e7;
fh = fopen(fname, 'w');
for i = 1:N
fprintf(fh, '%010d\n', i);
end
fclose(fh);
% count by fgetl()
tic
fh = fopen(fname, 'r');
n1 = 0;
while ~feof(fh)
s = fgetl(fh);
n1 = n1 + 1;
end
fclose(fh);
toc
% count by chunks
tic
fh = fopen(fname, 'r');
chunksize = 1e6;
n2 = 0;
while ~feof(fh)
ch = fread(fh, chunksize, 'uchar');
if isempty(ch)
break
end
n2 = n2 + sum(ch == char(10));
end
fclose(fh);
toc
N
n1
n2
==========================================
Elapsed time is 457.312000 seconds.
Elapsed time is 7.531000 seconds.
N =
10000000
n1 =
10000000
n2 =
10000000
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