looping trough files

BackwardsDown · 02-06-2007, 01:21 PM

Hi,

I am trying to make some sort of music-library program with C++. But now I have this pretty stupid question.

I want to read every id3-tag in a directory. So that means I need to loop recursively trough all of the files. But how would I do that?

Basically I need something like:

Code:

string filename;
loop {
   filename = next_file();
   // do something with the file
}

I was wandering to just do: ls >> file
And then readout the output line by line, but this seems to be very hard, at least harder than it should be.

matthewg42 · 02-06-2007, 01:30 PM

There are two main ways to get lists of files from directories:

1. readdir, opendir, closedir

2. glob.h

See the readdir and glob manual pages for details.

Once you've got the file names, I would guess the best thing would be to use some pre-existing open source tag processing library to do the actual extraction of the tags. I'm sure there are many alternative ID3 tag processing libraries out there - try a few and compare the performance - this is the sort of thing where different implementations can have wildly different performance characteristics.

BackwardsDown · 02-06-2007, 01:31 PM

Yes I already can read id3 tags from files. But until now I needed to type the name of the file's directly into the source code.

BackwardsDown · 02-09-2007, 09:33 AM

Quote:

1. readdir, opendir, closedir

I have now found a simple examle of how I can display the contents of a directory:

Code:

#include <errno.h>
#include <dirent.h>
#include <stdio.h>
#include <stdlib.h>
#include <iostream>

int main()
{
	DIR *pdir;
	struct dirent *pent;

	pdir=opendir("."); //"." refers to the current dir
	if (!pdir){
		std::cout << "opendir() failure; terminating\n";
		exit(1);
	}
	
	errno=0;
	while ((pent=readdir(pdir)))
	{
		std::cout << pent->d_name << "\n";
	}
	
	if (errno)
	{
		std::cout << "readdir() failure; terminating\n";
	exit(1);
	}
	
	closedir(pdir);
}

The output is as following:

Quote:

.
..
Makefile
.deps
readdir.o
.libs
readdir
a_directory
Press Enter to continue!

But how can I see the difference between a normal file and a directory?

Also, I dont seem to have a file called dir.h in my /usr/include/ or anywhere else.

kshkid · 02-09-2007, 10:39 PM

Difference between file and directory can be obtained by reading the contents of the directory. Do a stat on the directory and with that we can identify it as a directory or a file