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

# getdtablesize(3)

get file descriptor table size

## NAME

getdtablesize - get file descriptor table size

## LIBRARY

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

## SYNOPSIS

```
#include <unistd.h>
```

**int getdtablesize(void);**

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

**getdtablesize**():

```
    Since glibc 2.20:
        _DEFAULT_SOURCE || ! (_POSIX_C_SOURCE >= 200112L)
    glibc 2.12 to glibc 2.19:
        _BSD_SOURCE || ! (_POSIX_C_SOURCE >= 200112L)
    Before glibc 2.12:
        _BSD_SOURCE || _XOPEN_SOURCE >= 500
```

## DESCRIPTION

**getdtablesize**() returns the maximum number of files a process can have open, one more than the largest possible value for a file descriptor.

## RETURN VALUE

The current limit on the number of open files per process.

## ERRORS

On Linux, **getdtablesize**() can return any of the errors described for [**getrlimit**(2)](/getrlimit/2.md); see VERSIONS below.

## ATTRIBUTES

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

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **getdtablesize**() | Thread safety | MT-Safe |

## VERSIONS

The glibc version of **getdtablesize**() calls [**getrlimit**(2)](/getrlimit/2.md) and returns the current **RLIMIT\_NOFILE** limit, or **OPEN\_MAX** when that fails.

Portable applications should employ *sysconf(\_SC\_OPEN\_MAX)* instead of this call.

## STANDARDS

None.

## HISTORY

SVr4, 4.4BSD (first appeared in 4.2BSD).

## SEE ALSO

[**close**(2)](/close/2.md), [**dup**(2)](/dup/2.md), [**getrlimit**(2)](/getrlimit/2.md), [**open**(2)](/open/2.md)