getdtablesize (2) Linux Manual Page

getdtablesize – get file descriptor table size

Synopsis

#include <unistd.h>

int getdtablesize(void);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

getdtablesize():

Since glibc 2.12:

/* Glibc since 2.19: */ _DEFAULT_SOURCE

 || /* Glibc versions <= 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); see NOTES below.

Attributes

For an explanation of the terms used in this section, see attributes(7).

Interface	Attribute	Value
getdtablesize()	Thread safety	MT-Safe

Conforming To

SVr4, 4.4BSD (the getdtablesize() function first appeared in 4.2BSD). It is not specified in POSIX.1; portable applications should employ sysconf(_SC_OPEN_MAX) instead of this call.

Notes

getdtablesize() is implemented as a libc library function. The glibc version calls getrlimit(2) and returns the current RLIMIT_NOFILE limit, or OPEN_MAX when that fails.

See Also

close(2), dup(2), getrlimit(2), open(2)

Colophon

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