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FFS(3)                     Library Functions Manual                     FFS(3)

NAME
     ffs ffsl ffsll - find first bit set in a bit string

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <strings.h>

     int
     ffs(int value);

     ffsl(long value);

     ffsll(long long value);

DESCRIPTION
     The ffs(), ffsl(), and ffsll() functions find the first bit set in value
     and return the index of that bit.  Bits are numbered starting from 1,
     starting at the right-most bit.  A return value of 0 means that the
     argument was zero.

SEE ALSO
     bitstring(3), ffs32(3), ffs64(3), popcount(3)

STANDARDS
     The ffs() function conforms to IEEE Std 1003.1-2001 ("POSIX.1").  The
     ffsl() and ffsll() functions conform to IEEE Std 1003.1-2024 ("POSIX.1").

HISTORY
     The ffs() function appeared in 4.3BSD.  The prototype for it existed
     previously in the <string.h> header before it was moved to <strings.h>
     for POSIX compliance.

NetBSD 11.99                   November 1, 2024                   NetBSD 11.99