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RAND(3)               DragonFly Library Functions Manual               RAND(3)


rand, srand, sranddev, rand_r -- bad random number generator


Standard C Library (libc, -lc)


#include <stdlib.h> void srand(unsigned seed); void sranddev(void); int rand(void); int rand_r(unsigned *ctx);


These interfaces are obsoleted by random(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 ctx must be supplied by the caller.


arc4random(3), random(3), random(4)


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. DragonFly 3.5 May 25, 1999 DragonFly 3.5

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