Filter directory search results.

Hi all, I have a function that returns the contents of a directory in a string vector. It works perfectly but what I want to do is filter out the results for a certain file type. I just wanted to know if there was anything already available to do this? Or would I just have to take the last 4 characters of the string and compare it? Below is the function I am using to get the contents of a directory.

Code:

int getdir (std::string dir, std::vector<std::string> &files)
{
    DIR *dp;
    struct dirent *dirp;
    if((dp  = opendir(dir.c_str())) == NULL) {
        std::cout << "Error(" << errno << ") opening " << dir << std::endl;
        return errno;
    }

    while ((dirp = readdir(dp)) != NULL) {
        files.push_back(std::string(dirp->d_name));
    }
    closedir(dp);
    return 0;
}

EDIT:
I have come up with this... but its not perfect… but it works…
so again, is there a better way to do this?

Code:

int getdir (std::string dir, std::vector<std::string> &files, std::string filetype)
{
    DIR *dp;
    struct dirent *dirp;
    if((dp  = opendir(dir.c_str())) == NULL) {
        std::cout << "Error(" << errno << ") opening " << dir << std::endl;
        return errno;
    }

    while ((dirp = readdir(dp)) != NULL) {
        if (std::string(dirp->d_name).find(filetype)!=std::string::npos)
           files.push_back(std::string(dirp->d_name));
    }
    closedir(dp);
    return 0;
}

I would suggest substr so that you're comparing to the end instead of searching the whole string. If you''re looking for .txt files, foo.txt.bar would match with the current function

ok so i have come up with this...

Code:

int getdir (std::string dir, std::vector<std::string> &files, std::string filetype)
{
    DIR *dp;
    struct dirent *dirp;
    if((dp  = opendir(dir.c_str())) == NULL) {
        std::cout << "Error(" << errno << ") opening " << dir << std::endl;
        return errno;
    }

    while ((dirp = readdir(dp)) != NULL) {
        if (std::string(dirp->d_name).substr((std::string(dirp->d_name).length()-filetype.length()),filetype.length()).find(filetype)!= std::string::npos )
           files.push_back(std::string(dirp->d_name));
    }
    closedir(dp);
    return 0;
}

it compiles fine, but when i try to run it i get this error...

Code:

This application has requested the Runtime to terminate it in an unusual way.
Please contact the application's support team for more information.

Wearing the hat of guessing, I would suspect that

Code:

std::string(dirp->d_name).length()-filetype.length())

becomes negative - for example, the filename "." and ".." to be shorter than some filetypes.

As a side note:
std::string(dirp->d_name) is repeated three times in this line:

Code:

if (std::string(dirp->d_name).substr((std::string(dirp->d_name).length()-filetype.length()),filetype.length()).find(filetype)!= std::string::npos )
           files.push_back(std::string(dirp->d_name));

You should probably create a temporary variable.

--
Mats

Just a recommendation for the boost::filesystem library if you're going to do a lot of this kind of work.

Originally Posted by matsp

Wearing the hat of guessing, I would suspect that

Code:

std::string(dirp->d_name).length()-filetype.length())

becomes negative - for example, the filename "." and ".." to be shorter than some filetypes.

As a side note:
std::string(dirp->d_name) is repeated three times in this line:

Code:

if (std::string(dirp->d_name).substr((std::string(dirp->d_name).length()-filetype.length()),filetype.length()).find(filetype)!= std::string::npos )
           files.push_back(std::string(dirp->d_name));

You should probably create a temporary variable.

--
Mats

Ah cheers for that. if I use that function with out the file type filtering the first two results are always “.” and “..”

How could I get past this problem?

Originally Posted by rags_to_riches

Just a recommendation for the boost::filesystem library if you're going to do a lot of this kind of work.

Cheers that looks good… ill have a read of that, but I still wouldn’t mind trying to get this other function I have to work.

Originally Posted by Loic

Ah cheers for that. if I use that function with out the file type filtering the first two results are always “.” and “..”

How could I get past this problem?

Use rfind?

Originally Posted by Loic

Ah cheers for that. if I use that function with out the file type filtering the first two results are always “.” and “..”

How could I get past this problem?

Just put up a check comparing the string to . and .. before doing anything else

Originally Posted by Loic

Ah cheers for that. if I use that function with out the file type filtering the first two results are always “.” and “..”

How could I get past this problem?

Perhaps check if the length of the string is shorter than the length of the extension you are looking for? Then it can not possibly be a match, so no point in trying.

--
Mats

Originally Posted by Kernel Sanders

Just put up a check comparing the string to . and .. before doing anything else

Yes, but that doesn't prevent other short directory/filenames from causing the same problem. If you are searching for .txt, and a file is called a.c (my common name when I copy code from this site, a.c or x.c or some such - then I know it's nothing meaningfull or important), then it's shorter than extension, so it's still a problem.

--
Mats

Originally Posted by matsp

Perhaps check if the length of the string is shorter than the length of the extension you are looking for? Then it can not possibly be a match, so no point in trying.

--
Mats

Cheers, Thats worked