Hmmm...Accessing the environment from a C++ program. Maybe?

Kroenecker · 09-29-2004, 01:03 AM

I want to write a short c++ program that asks a user for a path. I then want the program to scan the files in the path and write a list of those files into another file. I have only begun to do some programming in c++.

I essentially want to do (something similar to) ls /to/some/path >> file.txt. It would be really nice to get some pointers on how to filter out and have say files ending in .ogg be the only ones put into my file.txt.

I want this to run under linux (of course), but if there is a more generic way of doing this that would allow me to cross compile for windows that would be interesting to know too.

Any suggestions?

Sadrul · 09-29-2004, 01:46 AM

`opendir' the location, then `readdir' the files, `strstr' to determine if they are of type ogg, at the end, `closedir'. look into the man pages of the functions.

-- Adil

greg108 · 09-29-2004, 01:48 AM

#include <iostream>

using namespace std;

int main()
{
system("ls /some/path > myfile.txt");
}

Kroenecker · 09-29-2004, 02:00 AM

Great! Thanks for the quit replies. I never knew that I could so easily ... call to the system (if that is the way it's put

) using "system." As far as using opendir and readdir those seem like more mind expanding options so I think I will try those too. Just for fun.

Kroenecker · 09-29-2004, 02:04 AM

One more question. I just looked at man opendir and (I haven't gotten to this in c++ class yet so yes it is premature but>>>) how would I do error handling for opendir?

Would I use some kind of if statement?

(From man opendir)

ERRORS
EACCES Permission denied.

EMFILE Too many file descriptors in use by process.

ENFILE Too many files are currently open in the system.

ENOENT Directory does not exist, or name is an empty string.

ENOMEM Insufficient memory to complete the operation.

ENOTDIR
name is not a directory.

If ( something (im not sure what!) == ENFILE) return ENFILE;

Or something similar?

itsme86 · 09-29-2004, 02:12 AM

Just above those error codes you listed is this in 'man opendir':

Code:

RETURN VALUE
       The opendir() function returns a pointer to the  directory
       stream or NULL if an error occurred.

So you'd do something like this:

Code:

dir = opendir("/some/path");
if(dir == NULL)
  cout << "An error occured!" << endl;
else
  cout << "We opened it successfully!" << endl;

Kroenecker · 09-29-2004, 02:15 AM

Right-o. Thanks

Sadrul · 09-29-2004, 02:19 AM

expanding from itsme86's code:

Code:

if(dir == NULL)
{
    cout << "An error occured!" << endl;
    cout << strerror(errno) << endl;
}

this will show just what the error is. (you will have to include `errno.h' file.

-- Adil