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 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 │
       └─────────────────────────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

STANDARDS
       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 man-pages 6.03                                         2023-02-05                                            getdtablesize(3)