_SC_CLK_TCK
tpm = sysconf(_SC_CLK_TCK) * 60;
case _SC_CLK_TCK:
hz_usecs = (int)(1000000 / sysconf(_SC_CLK_TCK));
{ "CLK_TCK", SYSCONF, _SC_CLK_TCK },
int hz = (int)sysconf(_SC_CLK_TCK);