On 06/20/2013 07:10 AM, Gary Willoughby wrote:
I have a simple problem, I want to open a file and read data from it.
When the file changes, i will read more data. The trouble is i only want
to open the file once.
Here's the simplified code:
import core.thread;
import std.stdio;
void main(string[] args)
{
auto file = File("file.txt", "r");
string line;
writeln("First Read:");
while ((line = file.readln()) !is null)
{
write(line);
}
Thread.sleep(dur!("seconds")(5)); // <-- More data is appended to
the file while waiting here.
writeln("Second Read:");
while ((line = file.readln()) !is null) // <-- Error! New data is
not read!
{
write(line);
}
}
I read the file, then when its paused, i add new lines to the opened
file. When the program resumes it totally ignores the new lines. doh!
I guess this is the result of buffering somewhere so i've tried all
sorts to try and escape this behaviour, including:
file.clearerr()
file.seek()
file.flush()
Nothing seems to work. What am i missing? It must be something simple.
Any ideas?
This must be platform-dependent. Your program works as expected under my
Scientific Linux distribution. (Same as Red Hat.)
I have tried four kinds of modifications to the file:
1) Append a new line: works as expected
echo new line >> file.txt
2) Overwrite the same file: works as expected
echo new content > file.txt
3) Delete the file and recreate: works as expected
rm file.txt; echo new content > file.txt
4) Rename the file: works better than expected :)
mv file.txt file2.txt; echo new line >> file2.txt
In any case, there must be lots to learn from the 'tail' utility. Its
'-f' command line switch achieves what you need, and '-F' achieves more
than what you need:
http://git.savannah.gnu.org/cgit/coreutils.git/tree/src/tail.c
Ali
