[C]Strings' array goes crazy.

[militandri]

Hi everyone. I wrote a function that should copy in a strings' array all the name of several files contained in a folder.

void get_filenames(char dir[]){
int i=0;
DIR *sd;

sd = opendir(dir);
struct dirent \*dird;

printf("\\nLa cartella %s contiene %d files.", dir, n\_files);    //"Folder %s contains %d files."
	
seekdir(sd, 2);

for(i=0;id\_name;
	printf("\\n%s", filenames\[i\]);
}

closedir(sd);

}

When I call this function it seems to be alright, and the printf contained in the for cicle prints the names of files correctly... But if I try to print these names somewhere out of this function, I see that each string of filenames[] contains the last string printed in the get_filenames function, that is the last file in the folder. I allocated filenames[] in another void function, this way:

...
filenames = malloc(n_files * sizeof(char));
for(i=0;i

[Freak30]

The line filenames = malloc(n_files * sizeof(char)); should be filenames = malloc(n_files * sizeof(char *)); because you use it to allocate pointers. You don't show the declaration of filenames in the sample, but I assume it's char **. By the way, what happens if a file in the directory has a name longer than 19 characters?

The good thing about pessimism is, that you are always either right or pleasently surprised.

[enhzflep]

I think you'll find that the line:

filenames[i]=dird->d_name;

should actually be something like:

filenames[i]=strdup(dird->d_name);

You see, dird->d_name is a location in memory that the current file's name is copied to - _but_ this location doesn't change, only the contents of the text does. What your code does is set each of the filename[] elements to hold this location. In the next iteration of the loop, the text contained there changes, but the location doesn't. So you've got all elements of filename[] holding the same address of a string. If, on the other-hand, you make a duplicate of the string in dird->d_name and then store _that_ location into filenames[], each element of filenames[] will point to a different location in memory - locations that contain the string you're after. Note - you should also change your last code-block.

filenames = malloc(n_files * sizeof(char*) );

So, 1) filenames should be a char** (I expect you've got it setup to be a char* currently) 2) each element (a char*) should contain the address of the duplicated string 3) No need for the filenames[i] = malloc(20 * sizeof(char) ); code.

[militandri]

Thank you for the answer. Of course I declared filenames as char**... :cool: But I didn't know really good how the d_name variable works, then I made some mistakes... Now it's all clearer!

[enhzflep]

You're welcome. I'd hoped you had, though the way you used it gave me the impression it was only a char* Glad to be of help. :)