Question

I try to write program where part of it is listing all directories (especially starting from /), but I have a problem with /proc/self which is infinitely recursive (I get /proc/self/task/4300/fd/3/proc/self/task/4300/fd/3/proc/self/task/4300/fd/3/proc/… and so on). What is nice way to deal with it?

EDIT: Program is written in C language and I use opendir(), readdir()

Answer 1

You can use the S_ISLNK macro to test the st_mode field returned by a call to lstat. If the file is a symbolic link, do not try to follow it.

[user@machine:~]:./list | grep link
/proc/mounts is a symbolic link
/proc/self is a symbolic link

Example code

#include <stdio.h>     // For perror
#include <stdlib.h>
#include <sys/types.h> // For stat, opendir, readdir
#include <sys/stat.h>  // For stat
#include <unistd.h>    // For stat
#include <dirent.h>    // For opendir, readdir

const char *prefix = "/proc";

int main(void)
{
    DIR *dir;
    struct dirent *entry;
    int result;
    struct stat status;
    char path[PATH_MAX];

    dir = opendir(prefix);
    if (!dir)
    {
        perror("opendir");
        exit(1);
    }

    entry = readdir(dir);
    while (entry)
    {
        result = snprintf(path, sizeof(path), "%s", prefix);
        snprintf(&path[result], sizeof(path) - result, "/%s", entry->d_name);
        printf("%s", path);

        result = lstat(path, &status);
        if (-1 == result)
        {
            printf("\n");
            perror("stat");
            exit(2);
        }

        if (S_ISLNK(status.st_mode))
        {
            printf("%s", " is a symbolic link");
        }

        printf("\n");

        entry = readdir(dir);
    }

    return(0);
}