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GETDTABLESIZE(3) Linux Programmer's Manual GETDTABLESIZE(3)
NAME
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 2.20:
_DEFAULT_SOURCE || ! (_POSIX_C_SOURCE >= 200112L)
Glibc 2.12 to 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
The glibc version of getdtablesize() 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)
Linux 2021-03-22 GETDTABLESIZE(3)