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#define _DEFAULT_SOURCE
#include <dirent.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
struct filtered_dir_entries {
struct dirent ** entries;
size_t entries_num;
};
static int search_dir(const char * const dir,
int (*filter_fn)(const struct dirent *),
struct filtered_dir_entries * const entries)
{
struct dirent **names;
int n;
n = scandir(dir, &names, filter_fn, alphasort);
if (n < 0) {
perror("scandir");
return 1;
}
entries->entries = names;
entries->entries_num = n;
return 0;
}
static int dirent_filter_only_numeric(const struct dirent * ent)
{
char * end_ptr;
errno = 0;
strtoul(ent->d_name, &end_ptr, 10);
return (errno != 0 || *end_ptr == '\0');
}
static int search_procfs_fd(const char * const dir, const char * const subdir,
struct filtered_dir_entries * const entries)
{
char buf[BUFSIZ];
snprintf(buf, sizeof buf, "%s/%s/fd", dir ,subdir);
return search_dir(buf, dirent_filter_only_numeric, entries);
}
static ssize_t realpath_procfs_fd(const char * const dir, const char * const pid,
const char * const fd, char * dest, size_t siz)
{
char buf[BUFSIZ];
snprintf(buf, sizeof buf, "%s/%s/fd/%s", dir, pid, fd);
return readlink(buf, dest, siz);
}
static void free_filtered_dir_entries(struct filtered_dir_entries * const entries)
{
if (!entries->entries) {
return;
}
for (size_t i = 0; i < entries->entries_num; ++i) {
free(entries->entries[i]);
}
free(entries->entries);
entries->entries = NULL;
entries->entries_num = 0;
}
int main(int argc, char **argv)
{
struct filtered_dir_entries proc_pid_entries = {};
struct filtered_dir_entries proc_fd_entries = {};
ssize_t realpath_used;
char realpath[BUFSIZ];
(void) argc;
(void) argv;
if (search_dir("/proc", dirent_filter_only_numeric, &proc_pid_entries)) {
exit(EXIT_FAILURE);
}
for (size_t i = 0; i < proc_pid_entries.entries_num; ++i) {
if (search_procfs_fd("/proc", proc_pid_entries.entries[i]->d_name,
&proc_fd_entries)) {
continue;
}
for (size_t j = 0; j < proc_fd_entries.entries_num; ++j) {
realpath_used = realpath_procfs_fd("/proc",
proc_pid_entries.entries[i]->d_name,
proc_fd_entries.entries[j]->d_name,
&realpath[0], sizeof realpath);
if (realpath_used < 0) {
continue;
}
printf("%s: __%.*s__\n", proc_pid_entries.entries[i]->d_name, (int)realpath_used, realpath);
}
free_filtered_dir_entries(&proc_fd_entries);
}
free_filtered_dir_entries(&proc_pid_entries);
}
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