linux man page for getdtablesize

GETDTABLESIZE(3)					     Linux Programmer's Manual						  GETDTABLESIZE(3)

NAME
       getdtablesize - get 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:
	       _BSD_SOURCE ||
		   !(_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600)
	   Before glibc 2.12:
	       _BSD_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED

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

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.1-2001;  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)

Linux								    2015-03-02							  GETDTABLESIZE(3)