FFS(3P) POSIX Programmer's Manual FFS(3P)PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding
Linux manual page for details of Linux behavior), or the interface may
not be implemented on Linux.
NAMEffs — find first set bit
int ffs(int i);
The ffs() function shall find the first bit set (beginning with the
least significant bit) in i, and return the index of that bit. Bits are
numbered starting at one (the least significant bit).
The ffs() function shall return the index of the first bit set. If i is
0, then ffs() shall return 0.
No errors are defined.
The following sections are informative.
The Base Definitions volume of POSIX.1‐2008, <strings.h>
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
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IEEE/The Open Group 2013 FFS(3P)