GETDTABLESIZESection: Linux Programmer's Manual (2)
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NAMEgetdtablesize - get descriptor table size
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
DESCRIPTIONgetdtablesize() returns the maximum number of files a process can have open, one more than the largest possible value for a file descriptor.
RETURN VALUEThe current limit on the number of open files per process.
ERRORSOn Linux, getdtablesize() can return any of the errors described for getrlimit(2); see NOTES below.
CONFORMING TOSVr4, 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.
NOTESgetdtablesize() 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. The libc4 and libc5 versions return OPEN_MAX (set to 256 since Linux 0.98.4).
SEE ALSOclose(2), dup(2), getrlimit(2), open(2)
COLOPHONThis page is part of release 3.21 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.