rand(3C) rand(3C)
NAME
rand(), rand_r(), srand() - simple random-number generator
SYNOPSIS
DESCRIPTION
uses a multiplicative, congruential, random-number generator with period 2^32 that returns successive pseudo-random numbers in the range
from 0 to 2^15-1.
can be called at any time to reset the random-number generator to a random starting point. The generator is initially seeded with a value
of 1.
returns a random number at the address pointed to by the randval parameter. The seed parameter can be set at any time to start the random-
number generator at an arbitrary point.
Note
The spectral properties of leave a great deal to be desired. provides a much better, though more elaborate, random-number generator (see
drand48(3C)).
RETURN VALUE
If seed or randval is NULL, returns 0. Otherwise, returns a psuedo-random integer.
EXAMPLES
The following:
int x, y;
srand(10);
x = rand();
y = rand();
would produce the same results as:
int x, y, s = 10;
x=rand_r(&s);
y=rand_r(&s);
WARNINGS
Users of should note that rand_r() now conforms with POSIX.1c. The old prototype of is supported for compatibility with existing DCE
applications only.
SEE ALSO
drand48(3C), random(3M), thread_safety(5), random(7).
STANDARDS CONFORMANCE
rand(3C)
