---
name: "readdir_r"
section: "3"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/readdir_r"
---

# readdir\_r(3)

read a directory

## NAME

readdir\_r - read a directory

## LIBRARY

Standard C library (*libc*, *-lc*)

## SYNOPSIS

```
#include <dirent.h>
```

**\[\[deprecated\]\] int readdir\_r(DIR \*restrict** *dirp***,**                              **struct dirent \*restrict** *entry***,**                              **struct dirent \*\*restrict** *result***);**

Feature Test Macro Requirements for glibc (see [**feature\_test\_macros**(7)](/feature_test_macros/7.md)):

**readdir\_r**():

```
    _POSIX_C_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
```

## DESCRIPTION

This function is deprecated; use [**readdir**(3)](/readdir/3.md) instead.

The **readdir\_r**() function was invented as a reentrant version of [**readdir**(3)](/readdir/3.md). It reads the next directory entry from the directory stream *dirp*, and returns it in the caller-allocated buffer pointed to by *entry*. For details of the *dirent* structure, see [**readdir**(3)](/readdir/3.md).

A pointer to the returned buffer is placed in *\*result*; if the end of the directory stream was encountered, then NULL is instead returned in *\*result*.

It is recommended that applications use [**readdir**(3)](/readdir/3.md) instead of **readdir\_r**(). Furthermore, since glibc 2.24, glibc deprecates **readdir\_r**(). The reasons are as follows:

- •

  On systems where **NAME\_MAX** is undefined, calling **readdir\_r**() may be unsafe because the interface does not allow the caller to specify the length of the buffer used for the returned directory entry.

- •

  On some systems, **readdir\_r**() can't read directory entries with very long names. When the glibc implementation encounters such a name, **readdir\_r**() fails with the error **ENAMETOOLONG** *after the final directory entry has been read*. On some other systems, **readdir\_r**() may return a success status, but the returned *d\_name* field may not be null terminated or may be truncated.

- •

  In the current POSIX.1 specification (POSIX.1-2008), [**readdir**(3)](/readdir/3.md) is not required to be thread-safe. However, in modern implementations (including the glibc implementation), concurrent calls to [**readdir**(3)](/readdir/3.md) that specify different directory streams are thread-safe. Therefore, the use of **readdir\_r**() is generally unnecessary in multithreaded programs. In cases where multiple threads must read from the same directory stream, using [**readdir**(3)](/readdir/3.md) with external synchronization is still preferable to the use of **readdir\_r**(), for the reasons given in the points above.

- •

  It is expected that a future version of POSIX.1 will make **readdir\_r**() obsolete, and require that [**readdir**(3)](/readdir/3.md) be thread-safe when concurrently employed on different directory streams.

## RETURN VALUE

The **readdir\_r**() function returns 0 on success. On error, it returns a positive error number (listed under ERRORS). If the end of the directory stream is reached, **readdir\_r**() returns 0, and returns NULL in *\*result*.

## ERRORS

- **EBADF**

  Invalid directory stream descriptor *dirp*.

- **ENAMETOOLONG**

  A directory entry whose name was too long to be read was encountered.

## ATTRIBUTES

For an explanation of the terms used in this section, see [**attributes**(7)](/attributes/7.md).

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **readdir\_r**() | Thread safety | MT-Safe |

## STANDARDS

POSIX.1-2008.

## HISTORY

POSIX.1-2001.

## SEE ALSO

[**readdir**(3)](/readdir/3.md)