Thread: reading multiple file names & displaying them

hi,
wondering if someone could explain why the following doesn't work as intended ?
The 2nd for loop should display the file names, but instead it displays the same one, the last one read in.
Now I've tested reading in strings into char array and displaying them again in another for loop, and it works as intended, and I've looked/compared the addresses too but this, has me stumped.

Something I'm missing?

Code:

#include <dirent.h> 
#include <iostream>
using namespace std;

int main()
{
char *afilelist[100] = { "0" };
DIR  					*d;
struct dirent *dir[100];
d = opendir(".");

if (d)
{
	for( int x=0; (dir[x] = readdir(d)) != NULL;x++)
	{
		afilelist[x] = dir[x]->d_name;
		cout<<afilelist[x]<<endl; //displays file names properly.
	}
closedir(d);
}

cout<<endl;
for( int x=0;x<10 ; x++)
{
	cout<<afilelist[x]<<endl; //doesn't display file names as per the array ?
}

cin.get();
}

If I run the code & return the addresses (and what it returns, is next to it);

First for loop;
0x22fd70 .
0x22fd74 ..
0x22fd78 file1name.txt
0x22fd7c file2name.txt
0x22fd80 fileXname.ext
0x22fd84 fileLast.ext

2nd for loop, the addresses are the same as first, however what it returns is not
0x22fd70 fileLast.ext
0x22fd74 fileLast.ext
0x22fd78 fileLast.ext
0x22fd7c fileLast.ext
It's only displaying/showing the last read in file name.

Now if I do this with some simple char/string array and do the same thing, I don't have the same problem. So I don't understand why the problem is happening with this code.

Originally Posted by King Mir

....while 100 is surely a high enough....

My code is just for my own testing/learning.

Looks like you need to copy the directory names into an array of strings, instead of keeping a pointer. I recommend using an array of std::string instead of char *.

Thanks, changing that worked. However, could you/someone possibly explain why the above code doesn't work as intended but the following does;

Code:

#include <iostream>
using namespace std;

int main()
{
	char *aChar[15] = { "0" };
	char *cString[] = {"one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten", "end" };

for(int i=0; cString[i]<"end" ; i++)
{
	aChar[i] = cString[i];
}

for(int i=0; cString[i]<"end"; i++)
{
	cout<<aChar[i]<<endl; //displays array as intended
}

cin.get();
}

Use strcmp in a while loop like strcmp("end", cString[i]) != 0

Originally Posted by Dino

If you look at the addresses returned from the readdir() function you posted above, they are only 4 bytes apart. Apparently, readdir() on your system does not guarantee to preserve the contents of the structure across subsequent calls.

This works on my system (a Mac). See how it runs on yours.

Works on mine, but again the 2nd for loop only displays the last or most recent filename read in.

Code:

for(int i=0; cString[i]<"end" ; i++)

is comparing the addresses and not the values.

Really? But if one displays what cString[i] is, it shows/returns the value yes? How is that comparing addresses if "end" is a string literal?

Thanks.