Updated: 2021/Apr/14

ILOG2(3) Library Functions Manual ILOG2(3)NAMEilog2- integer logarithmSYNOPSIS#include<sys/bitops.h>sizeilog2(size x);DESCRIPTIONTheilog2() macro returns an integer (binary) logarithm of x. It is the logarithm for base 2; the binary logarithm of x is the power to which the number 2 must be raised to obtain the value x. The type of the input parameter should be either uint32_t or uint64_t.ERRORSA value -1 is returned on error.SEEALSObitops(3), ilogb(3), log2(3), imax(9), powerof2(9)HISTORYTheilog2() macro first appeared in NetBSD 5.0. NetBSD 9.99 May 10, 2011 NetBSD 9.99