...
Compliant Solution (POSIX)
This complian compliant solution replaces the rand() function with the POSIX random() function:
...
Although not specified by POSIX, arc4random() is another possibility for systems that support it. The arc4random(3) manual page [OpenBSD] states:
... provides higher quality of data than those described in rand(3), random(3), and drand48(3).
...