NAME
rand, srand
— bad random number
generator
SYNOPSIS
#include
<stdlib.h>
void
srand(unsigned
int seed);
int
rand(void);
int
rand_r(unsigned
int *seed);
DESCRIPTION
The
rand()
function computes a sequence of pseudo-random integers in the range of 0 to
RAND_MAX (as defined by the header file
⟨stdlib.h⟩).
The
srand()
function sets its argument as the seed for a new sequence of pseudo-random
numbers to be returned by rand(). These sequences
are repeatable by calling srand() with the same seed
value.
If no seed value is provided, the functions are automatically seeded with a value of 1.
The
rand_r() is
a thread-safe version of rand(). Storage for the
seed must be provided through the seed argument, and
needs to have been initialized by the caller.
SEE ALSO
STANDARDS
The rand() and
srand() functions conform to ANSI
X3.159-1989 (“ANSI C89”).
The rand_r() function conforms to
IEEE Std 1003.1-2008 (“POSIX.1”).
HISTORY
The functions rand() and
srand() first appeared in
Version 3 AT&T UNIX.