CLOCK(3) BSD Library Functions Manual CLOCK(3)NAMEclock — determine processor time used
Standard C Library (libc, -lc)
The clock() function determines the amount of processor time used since
the invocation of the calling process, measured in CLOCKS_PER_SECs of a
The clock() function returns the amount of time used unless an error
occurs, in which case the return value is -1.
SEE ALSOgetrusage(2), clocks(7)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 incompatibil‐
ity and one million is still inadequate on modern processors.
BSD June 4, 1993 BSD