opendir() — Open a directory

Standards

Standards / Extensions C or C++ Dependencies
POSIX.1
XPG4
XPG4.2
Single UNIX Specification, Version 3
 both  

Format

#define _POSIX_SOURCE
#include <dirent.h>

DIR *opendir(const char *dirname);

General description

Opens a directory so that it can be read with readdir() or __readdir2(). dirname is a string giving the name of the directory you want to open. The first readdir() or __readdir2() call reads the first entry in the directory.

Returned value

If successful, opendir() returns a pointer to a DIR object. This object describes the directory and is used in subsequent operations on the directory, in the same way that FILE objects are used in file I/O operations.

If unsuccessful, opendir() returns a NULL pointer and sets errno to one of the following values:
Error Code
Description
EACCES
The process does not have permission to search some component of dirname, or it does not have read permission on the directory itself.
ELOOP
A loop exists in the symbolic links. This error is issued if more than POSIX_SYMLOOP (defined in the limits.h header file) symbolic links are encountered during resolution of the dirname argument.
EMFILE
The process has too many other file descriptors already open.
ENAMETOOLONG
dirname is longer than PATH_MAX characters, or some component of dirname is longer than NAME_MAX characters while _POSIX_NO_TRUNC is in effect. For symbolic links, the length of the pathname string substituted for a symbolic link exceeds PATH_MAX. The PATH_MAX and NAME_MAX values can be determined using pathconf().
ENFILE
The entire system has too many other file descriptors already open.
ENOENT
The directory dirname does not exist.
ENOMEM
There is not enough storage available to open the directory.
ENOTDIR
Some component of the dirname pathname is not a directory.

Example

CELEBO01 
/* CELEBO01

   This example opens a directory.

 */
#define _POSIX_SOURCE
#include <dirent.h>
#include <errno.h>
#include <sys/stat.h>
#include <sys/types.h>
#undef _POSIX_SOURCE
#include <stdio.h>

void traverse(char *fn, int indent) {
  DIR *dir;
  struct dirent *entry;
  int count;
  char path[1025];
  struct stat info;

  for (count=0; count<indent; count++) printf("  ");
  printf("%s\n", fn);

  if ((dir = opendir(fn)) == NULL)
    perror("opendir() error");
  else {
    while ((entry = readdir(dir)) != NULL) {
      if (entry->d_name[0] != '.') {
        strcpy(path, fn);
        strcat(path, "/");
        strcat(path, entry->d_name);
        if (stat(path, &info) != 0)
          fprintf(stderr, "stat() error on %s: %s\n", path,
                  strerror(errno));
        else if (S_ISDIR(info.st_mode))
               traverse(path, indent+1);
      }
    }
    closedir(dir);
  }
}

main() {
  puts("Directory structure:");
  traverse("/etc", 0);
}
Output 
Directory structure:
/etc
  /etc/samples
    /etc/samples/IBM
  /etc/IBM

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