ffs(3) Library Functions Manual ffs(3) ffs, ffsl, ffsll - (libc -lc) #include int ffs(int i); int ffsl(long i); int ffsll(long long i); glibc ( feature_test_macros(7)): ffs(): glibc 2.12: _XOPEN_SOURCE >= 700 || ! (_POSIX_C_SOURCE >= 200809L) || /* glibc >= 2.19: */ _DEFAULT_SOURCE || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE glibc 2.12: ffsl(), ffsll(): glibc 2.27: _DEFAULT_SOURCE glibc 2.27: _GNU_SOURCE ffs() ( ) i. 1 32 64. ffsll() ffsl() . 0 i. attributes(7). +------------+------------------------------------+--------------------+ || | | +------------+------------------------------------+--------------------+ |ffs(), | | MT-Safe | |ffsl(), | | | |ffsll() | | | +------------+------------------------------------+--------------------+ ffs() POSIX.1-2001, POSIX.1-2008, 4.3BSD. ffsl() ffsll() GNU. memchr(3) 3 . . : . 6.18 8 2026 ffs(3)