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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.


NAME
       ffs — find first set bit


SYNOPSIS
       #include <strings.h>

       int ffs(int i);


DESCRIPTION
       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).


RETURN VALUE
       The  ffs()  function  shall  return  the index of the first bit set. If i is 0, then ffs()
       shall return 0.


ERRORS
       No errors are defined.

       The following sections are informative.


EXAMPLES
       None.


APPLICATION USAGE
       None.


RATIONALE
       None.


FUTURE DIRECTIONS
       None.


SEE ALSO
       The Base Definitions volume of POSIX.1‐2008, <strings.h>


COPYRIGHT
       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  Electrical  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 most likely to have
       been introduced during the conversion of the source files to man page  format.  To  report
       such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .