| .\" Copyright 1993 Rickard E. Faith (faith@cs.unc.edu) |
| .\" |
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| .\" Modified 2002-04-15 by Roger Luethi <rl@hellgate.ch> and aeb |
| .\" |
| .TH GETDTABLESIZE 3 2021-03-22 "Linux" "Linux Programmer's Manual" |
| .SH NAME |
| getdtablesize \- get file descriptor table size |
| .SH SYNOPSIS |
| .nf |
| .B #include <unistd.h> |
| .PP |
| .B int getdtablesize(void); |
| .fi |
| .PP |
| .RS -4 |
| Feature Test Macro Requirements for glibc (see |
| .BR feature_test_macros (7)): |
| .RE |
| .PP |
| .BR getdtablesize (): |
| .nf |
| 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 |
| .\" || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED |
| .fi |
| .SH DESCRIPTION |
| .BR getdtablesize () |
| returns the maximum number of files a process can have open, |
| one more than the largest possible value for a file descriptor. |
| .SH RETURN VALUE |
| The current limit on the number of open files per process. |
| .SH ERRORS |
| On Linux, |
| .BR getdtablesize () |
| can return any of the errors described for |
| .BR getrlimit (2); |
| see NOTES below. |
| .SH ATTRIBUTES |
| For an explanation of the terms used in this section, see |
| .BR attributes (7). |
| .ad l |
| .nh |
| .TS |
| allbox; |
| lbx lb lb |
| l l l. |
| Interface Attribute Value |
| T{ |
| .BR getdtablesize () |
| T} Thread safety MT-Safe |
| .TE |
| .hy |
| .ad |
| .sp 1 |
| .SH CONFORMING TO |
| SVr4, 4.4BSD (the |
| .BR getdtablesize () |
| function first appeared in 4.2BSD). |
| It is not specified in POSIX.1; |
| portable applications should employ |
| .I sysconf(_SC_OPEN_MAX) |
| instead of this call. |
| .SH NOTES |
| The glibc version of |
| .BR getdtablesize () |
| calls |
| .BR getrlimit (2) |
| and returns the current |
| .B RLIMIT_NOFILE |
| limit, or |
| .B OPEN_MAX |
| when that fails. |
| .\" The libc4 and libc5 versions return |
| .\" .B OPEN_MAX |
| .\" (set to 256 since Linux 0.98.4). |
| .SH SEE ALSO |
| .BR close (2), |
| .BR dup (2), |
| .BR getrlimit (2), |
| .BR open (2) |