rand, drand, irand - return random values
function irand (iflag)
function rand (iflag)
double precision function drand (iflag)
The newer random(3f) should be used in new applications; rand remains for compatibilty.
These functions use rand(3C) to generate sequences of random numbers. If iflag is '1', the generator is restarted and the first random
value is returned. If iflag is otherwise non-zero, it is used as a new seed for the random number generator, and the first new random
value is returned.
Irand returns positive integers in the range 0 through 2147483647. Rand and drand return values in the range 0. through 1.0 .
SEE ALSO random(3F), rand(3C)BUGS
The algorithm returns a 15 bit quantity on the PDP11; a 31 bit quantity on the VAX. Irand on the PDP11 calls rand(3C) twice to form a 31
bit quantity, but bit 15 will always be 0.
4.2 Berkeley Distribution May 15, 1985 RAND(3F)
Check Out this Related Man Page
RAND(3) BSD Library Functions Manual RAND(3)NAME
rand, rand_r, srand, sranddev -- bad random number generator
Standard C Library (libc, -lc)
These interfaces are obsoleted by arc4random(3).
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 seed 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 sranddev() function initializes a seed, using the random(4) random number device which returns good random numbers. However, the rand()
function still remains unsuitable for cryptographic use.
The rand_r() function provides the same functionality as rand(). A pointer to the context value seed must be supplied by the caller.
SEE ALSO arc4random(3), random(3), random(4)STANDARDS
The rand() and srand() functions conform to ISO/IEC 9899:1990 (``ISO C90'').
The rand_r() function is as proposed in the POSIX.4a Draft #6 document.
BSD May 25, 1999 BSD
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