Counting the number of files in a directory using C

No guarantee that this code compiles, and it's really only compatible with Linux and the BSDs:

#include <dirent.h>

...

int file_count = 0;
DIR * dirp;
struct dirent * entry;

dirp = opendir("path"); /* There should be error handling after this */
while ((entry = readdir(dirp)) != NULL) {
    if (entry->d_type == DT_REG) { /* If the entry is a regular file */
         file_count++;
    }
}
closedir(dirp);

See readdir.

If you want to include subdirectories as well, you can use this function that I'm using in some of my code. You should probably modify it to include some more error checking and support different directory separators.

int countfiles(char *path) {
    DIR *dir_ptr = NULL;
    struct dirent *direntp;
    char *npath;
    if (!path) return 0;
    if( (dir_ptr = opendir(path)) == NULL ) return 0;

    int count=0;
    while( (direntp = readdir(dir_ptr)))
    {
        if (strcmp(direntp->d_name,".")==0 ||
            strcmp(direntp->d_name,"..")==0) continue;
        switch (direntp->d_type) {
            case DT_REG:
                ++count;
                break;
            case DT_DIR:            
                npath=malloc(strlen(path)+strlen(direntp->d_name)+2);
                sprintf(npath,"%s/%s",path, direntp->d_name);
                count += countfiles(npath);
                free(npath);
                break;
        }
    }
    closedir(dir_ptr);
    return count;
}