Even using a clock could be insufficient on some systems. I can't
cite Unix examples, but here are some analogous cases that may
suggest possible problems.
1) In the late unlamented Primos's version of 'date', the seconds
would always be a multiple of 4. I observed this undocumented
'feature' when using the date to create random file names, and got
clashes when I ran a short function twice in rapid succession.
2) The book "One Million Random Digits with 100,000 Normal
Deviates" describes how using a clock to time radioactive decays
did not produce a uniform distribution of the least significant
digit. Probably the clock was lingering for a slightly different
amount of time on the different digits.
Nevertheless, clock input is certainly better than no clock input.
Wm. Randolph Franklin, wrf @
edu, (518) 276-6077; Fax: -6261
ECSE Dept., 6026 JEC, Rensselaer Polytechnic Inst, Troy NY, 12180 USA