Can't scan directory in order that files appear

Question

I'm trying to perform DFS on a folder that can contain sub folders. The goal is to locate all .txt files from a directory. I need to find the .txt files in the order that DFS finds them and preserve the order of files in a folder.

Currently my code for scanning a directory uses the scandir() function:

int n = scandir(path, &namelist, NULL, alphasort);

This sorts the files in a folder in alphabetical order, which isn't exactly what I want.

Edit: I've tried using opendir() and readdir() but this is accessing files in a seemingly random order.

Answer 1

According to versionsort man page

int versionsort(const void *a, const void *b);

can be passed as a callback to scandir() and is declared in dirent.h.

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First thing to check: "Feature Test Macro Requirements"

From the same page linked above:

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

scandir(), alphasort(): _BSD_SOURCE || _SVID_SOURCE

versionsort(): _GNU_SOURCE.

These macros need to be defined before dirent.h inclusion in order to enable the specific feature.

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Second thing to check: glibc version

From the same page linked above:

Versions

versionsort() was added to glibc in version 2.1.

Please refer to this question to learn how to check your glibc version.