How do you scan a directory for folders and files in C? It needs to be cross-platform.
9 Answers
The following POSIX program will print the names of the files in the current directory:
#define _XOPEN_SOURCE 700
#include <stdio.h>
#include <sys/types.h>
#include <dirent.h>
int main (void)
{
DIR *dp;
struct dirent *ep;
dp = opendir ("./");
if (dp != NULL)
{
while ((ep = readdir (dp)) != NULL)
puts (ep->d_name);
(void) closedir (dp);
return 0;
}
else
{
perror ("Couldn't open the directory");
return -1;
}
}
Credit: http://www.gnu.org/software/libtool/manual/libc/Simple-Directory-Lister.html
Tested in Ubuntu 16.04.

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What about this: `error: unknown type name 'off64_t'` – Tomáš Zato May 13 '14 at 11:12
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I had to change the `while` condition to `(ep = readdir(dp)) != NULL)` – jds Jan 08 '15 at 04:59
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@Clayton - what if I want to print just the .txt files? – jimo May 13 '15 at 13:17
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1For Windows, you may need the win32 implementation of dirent.h: https://github.com/tronkko/dirent . Just change
to "dirent.h" – bot1131357 Dec 11 '16 at 23:20
The strict answer is "you can't", as the very concept of a folder is not truly cross-platform.
On MS platforms you can use _findfirst, _findnext and _findclose for a 'c' sort of feel, and FindFirstFile and FindNextFile for the underlying Win32 calls.
Here's the C-FAQ answer:

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is there a alias already setup for _findfirst, _findnext and _findclose somewhere? not in windows.h right? – BuddyJoe Aug 14 '12 at 13:12
I've created an open source (BSD) C header that deals with this problem. It currently supports POSIX and Windows. Please check it out:
https://github.com/cxong/tinydir
tinydir_dir dir;
tinydir_open(&dir, "/path/to/dir");
while (dir.has_next)
{
tinydir_file file;
tinydir_readfile(&dir, &file);
printf("%s", file.name);
if (file.is_dir)
{
printf("/");
}
printf("\n");
tinydir_next(&dir);
}
tinydir_close(&dir);

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How does this help any more than the original system dependent implementations? Or is it so that you only need one named library for Windows and POSIX? – kevr Nov 08 '16 at 01:40
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@kevr: tinydir.h is a giant `#ifdef` solution in one convenient header file. – Joshua May 23 '19 at 01:42
There is no standard C (or C++) way to enumerate files in a directory.
Under Windows you can use the FindFirstFile/FindNextFile functions to enumerate all entries in a directory. Under Linux/OSX use the opendir/readdir/closedir functions.

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GLib is a portability/utility library for C which forms the basis of the GTK+ graphical toolkit. It can be used as a standalone library.
It contains portable wrappers for managing directories. See Glib File Utilities documentation for details.
Personally, I wouldn't even consider writing large amounts of C-code without something like GLib behind me. Portability is one thing, but it's also nice to get data structures, thread helpers, events, mainloops etc. for free
Jikes, I'm almost starting to sound like a sales guy :) (don't worry, glib is open source (LGPL) and I'm not affiliated with it in any way)

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opendir/readdir are POSIX. If POSIX is not enough for the portability you want to achieve, check Apache Portable Runtime

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Directory listing varies greatly according to the OS/platform under consideration. This is because, various Operating systems using their own internal system calls to achieve this.
A solution to this problem would be to look for a library which masks this problem and portable. Unfortunately, there is no solution that works on all platforms flawlessly.
On POSIX compatible systems, you could use the library to achieve this using the code posted by Clayton (which is referenced originally from the Advanced Programming under UNIX book by W. Richard Stevens). this solution will work under *NIX systems and would also work on Windows if you have Cygwin installed.
Alternatively, you could write a code to detect the underlying OS and then call the appropriate directory listing function which would hold the 'proper' way of listing the directory structure under that OS.

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The most similar method to readdir
is probably using the little-known _find
family of functions.

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You can find the sample code on the wikibooks link
/**************************************************************
* A simpler and shorter implementation of ls(1)
* ls(1) is very similar to the DIR command on DOS and Windows.
**************************************************************/
#include <stdio.h>
#include <dirent.h>
int listdir(const char *path)
{
struct dirent *entry;
DIR *dp;
dp = opendir(path);
if (dp == NULL)
{
perror("opendir");
return -1;
}
while((entry = readdir(dp)))
puts(entry->d_name);
closedir(dp);
return 0;
}
int main(int argc, char **argv) {
int counter = 1;
if (argc == 1)
listdir(".");
while (++counter <= argc) {
printf("\nListing %s...\n", argv[counter-1]);
listdir(argv[counter-1]);
}
return 0;
}

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