Navigating through files using dirent.h?

Question

I would like to know how I can navigate and edit folders and files through code in C. I have looked up the library dirent.h but I'm not sure which functions are used for traversing through directories. Am I even using the right library for this case, and if so, could you give a brief explanation of a few of the fundamental functions I will need to move around folders and change files. Also, do I have to use a pointer of some kind to keep track of which directory I am currently in, like I would with a linked list? Would I need to create a binary tree in order to have something that the pointer can point to?

score 8 · Accepted Answer · answered Aug 01 '14 at 02:49

The most important functions are:

opendir(const char *) - opens a directory and returns an object of type DIR

readdir(DIR *) - reads the content of a directory and returns an object of type dirent (struct)

closedir(DIR *) - closes a directory

For example, you can list the content of a directory using this code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <dirent.h>

char *pathcat(const char *str1, char *str2);

int main()
{
    struct dirent *dp;
    char *fullpath;
    const char *path="C:\\test\\"; // Directory target
    DIR *dir = opendir(path); // Open the directory - dir contains a pointer to manage the dir
    while (dp=readdir(dir)) // if dp is null, there's no more content to read
    {
        fullpath = pathcat(path, dp->d_name);
        printf("%s\n", fullpath);
        free(fullpath);
    }
    closedir(dir); // close the handle (pointer)
    return 0;
}

char *pathcat(const char *str1, char *str2)
{
    char *res;
    size_t strlen1 = strlen(str1);
    size_t strlen2 = strlen(str2);
    int i, j;
    res = malloc((strlen1+strlen2+1)*sizeof *res);
    strcpy(res, str1);
    for (i=strlen1, j=0; ((i<(strlen1+strlen2)) && (j<strlen2)); i++, j++)
        res[i] = str2[j];
    res[strlen1+strlen2] = '\0';
    return res;
}

The pathcat function simply concatenates 2 paths.

This code only scans the chosen directory (not its subdirectories). You must create your own code to perform an 'in-depth' scan (recursive function, etc.).

Note that `pathcat()` assumes the first path ends with an appropriate delimiter (separator; `'\\'` for Windows, or `'/'` for Unix), as it does in this code. A more general version would add the separator in the middle, but you'd need to adjust the memory allocation (add an extra character) to avoid overflow. The code might benefit from `sprintf()`; or it could use `memmove()` or `memcpy()` since you know the lengths of the strings. In fact, you should always know the lengths of the strings, so `memmove()` should always be an option. — Jonathan Leffler, Aug 01 '14 at 05:53

Navigating through files using dirent.h?

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