ffs(3) - NetBSD Manual Pages

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FFS(3)                  NetBSD 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 argu-
     ment 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 pre-
     viously in the <string.h> header before it was moved to <strings.h> for
     POSIX compliance.

NetBSD 10.99                   November 1, 2024                   NetBSD 10.99