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diff --git a/man3/rand.3 b/man3/rand.3 deleted file mode 100644 index 8dfd80fb1..000000000 --- a/man3/rand.3 +++ /dev/null @@ -1,243 +0,0 @@ -'\" t -.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk) -.\" -.\" SPDX-License-Identifier: Linux-man-pages-copyleft -.\" -.\" References consulted: -.\" Linux libc source code -.\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991) -.\" 386BSD man pages -.\" -.\" Modified 1993-03-29, David Metcalfe -.\" Modified 1993-04-28, Lars Wirzenius -.\" Modified 1993-07-24, Rik Faith (faith@cs.unc.edu) -.\" Modified 1995-05-18, Rik Faith (faith@cs.unc.edu) to add -.\" better discussion of problems with rand on other systems. -.\" (Thanks to Esa Hyyti{ (ehyytia@snakemail.hut.fi).) -.\" Modified 1998-04-10, Nicolás Lichtmaier <nick@debian.org> -.\" with contribution from Francesco Potorti <F.Potorti@cnuce.cnr.it> -.\" Modified 2003-11-15, aeb, added rand_r -.\" 2010-09-13, mtk, added example program -.\" -.TH rand 3 (date) "Linux man-pages (unreleased)" -.SH NAME -rand, rand_r, srand \- pseudo-random number generator -.SH LIBRARY -Standard C library -.RI ( libc ", " \-lc ) -.SH SYNOPSIS -.nf -.B #include <stdlib.h> -.PP -.B int rand(void); -.BI "void srand(unsigned int " seed ); -.PP -.BI "[[deprecated]] int rand_r(unsigned int *" seedp ); -.fi -.PP -.RS -4 -Feature Test Macro Requirements for glibc (see -.BR feature_test_macros (7)): -.RE -.PP -.BR rand_r (): -.nf - Since glibc 2.24: - _POSIX_C_SOURCE >= 199506L - glibc 2.23 and earlier - _POSIX_C_SOURCE -.fi -.SH DESCRIPTION -The -.BR rand () -function returns a pseudo-random integer in the range 0 to -.B RAND_MAX -inclusive (i.e., the mathematical range [0,\ \fBRAND_MAX\fR]). -.PP -The -.BR srand () -function sets its argument as the seed for a new -sequence of pseudo-random integers to be returned by -.BR rand (). -These sequences are repeatable by calling -.BR srand () -with the same seed value. -.PP -If no seed value is provided, the -.BR rand () -function is automatically seeded with a value of 1. -.PP -The function -.BR rand () -is not reentrant, since it -uses hidden state that is modified on each call. -This might just be the seed value to be used by the next call, -or it might be something more elaborate. -In order to get reproducible behavior in a threaded -application, this state must be made explicit; -this can be done using the reentrant function -.BR rand_r (). -.PP -Like -.BR rand (), -.BR rand_r () -returns a pseudo-random integer in the range [0,\ \fBRAND_MAX\fR]. -The -.I seedp -argument is a pointer to an -.I unsigned int -that is used to store state between calls. -If -.BR rand_r () -is called with the same initial value for the integer pointed to by -.IR seedp , -and that value is not modified between calls, -then the same pseudo-random sequence will result. -.PP -The value pointed to by the -.I seedp -argument of -.BR rand_r () -provides only a very small amount of state, -so this function will be a weak pseudo-random generator. -Try -.BR drand48_r (3) -instead. -.SH RETURN VALUE -The -.BR rand () -and -.BR rand_r () -functions return a value between 0 and -.B RAND_MAX -(inclusive). -The -.BR srand () -function returns no value. -.SH ATTRIBUTES -For an explanation of the terms used in this section, see -.BR attributes (7). -.ad l -.nh -.TS -allbox; -lbx lb lb -l l l. -Interface Attribute Value -T{ -.BR rand (), -.BR rand_r (), -.BR srand () -T} Thread safety MT-Safe -.TE -.hy -.ad -.sp 1 -.SH VERSIONS -The versions of -.BR rand () -and -.BR srand () -in the Linux C Library use the same random number generator as -.BR random (3) -and -.BR srandom (3), -so the lower-order bits should be as random as the higher-order bits. -However, on older -.BR rand () -implementations, and on current implementations on different systems, -the lower-order bits are much less random than the higher-order bits. -Do not use this function in applications intended to be portable -when good randomness is needed. -(Use -.BR random (3) -instead.) -.SH STANDARDS -.TP -.BR rand () -.TQ -.BR srand () -C11, POSIX.1-2008. -.TP -.BR rand_r () -POSIX.1-2008. -.SH HISTORY -.TP -.BR rand () -.TQ -.BR srand () -SVr4, 4.3BSD, C89, POSIX.1-2001. -.TP -.BR rand_r () -POSIX.1-2001. -Obsolete in POSIX.1-2008. -.SH EXAMPLES -POSIX.1-2001 gives the following example of an implementation of -.BR rand () -and -.BR srand (), -possibly useful when one needs the same sequence on two different machines. -.PP -.in +4n -.EX -static unsigned long next = 1; -\& -/* RAND_MAX assumed to be 32767 */ -int myrand(void) { - next = next * 1103515245 + 12345; - return((unsigned)(next/65536) % 32768); -} -\& -void mysrand(unsigned int seed) { - next = seed; -} -.EE -.in -.PP -The following program can be used to display the -pseudo-random sequence produced by -.BR rand () -when given a particular seed. -When the seed is -.IR \-1 , -the program uses a random seed. -.PP -.in +4n -.\" SRC BEGIN (rand.c) -.EX -#include <stdio.h> -#include <stdlib.h> -\& -int -main(int argc, char *argv[]) -{ - int r; - unsigned int seed, nloops; -\& - if (argc != 3) { - fprintf(stderr, "Usage: %s <seed> <nloops>\en", argv[0]); - exit(EXIT_FAILURE); - } -\& - seed = atoi(argv[1]); - nloops = atoi(argv[2]); -\& - if (seed == \-1) { - seed = arc4random(); - printf("seed: %u\en", seed); - } -\& - srand(seed); - for (unsigned int j = 0; j < nloops; j++) { - r = rand(); - printf("%d\en", r); - } -\& - exit(EXIT_SUCCESS); -} -.EE -.\" SRC END -.in -.SH SEE ALSO -.BR drand48 (3), -.BR random (3) |