| CLOCK(3) |
FreeBSD Library Functions Manual |
CLOCK(3) |
NAME
clock —
determine processor time used
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include < time.h>
clock_t
clock( void);
DESCRIPTION
The
clock() function determines the amount of processor time used since the invocation of the calling process, measured in
CLOCKS_PER_SECs of a second.
RETURN VALUES
The
clock() function returns the amount of time used unless an error occurs, in which case the return value is -1.
STANDARDS
The
clock() function conforms to ISO/IEC 9899:1990 (“ISO C90”). However, Version 2 of the Single UNIX Specification (“SUSv2”) requires
CLOCKS_PER_SEC to be defined as one million.
FreeBSD does not conform to this requirement; changing the value would introduce binary incompatibility and one million is still inadequate on modern processors.