getdtablesize(3)	    Library Functions Manual		getdtablesize(3)

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)):

     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  getr-
     limit(2); see VERSIONS below.

ATTRIBUTES
     For  an  explanation  of the terms used in this section, see attributes(7).
     allbox; lbx lb lb l l l.  Interface Attribute Value T{ getdtablesize()
     T}	  Thread safety	  MT-Safe

VERSIONS
     The glibc version of getdtablesize() calls	 getrlimit(2)  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), dup(2), getrlimit(2), open(2)

Linux man-pages 6.18		   2026-02-08			getdtablesize(3)