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diff --git a/man3/random.3 b/man3/random.3 new file mode 100644 index 000000000..37e53e9ae --- /dev/null +++ b/man3/random.3 @@ -0,0 +1,91 @@ +.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk) +.\" +.\" Permission is granted to make and distribute verbatim copies of this +.\" manual provided the copyright notice and this permission notice are +.\" preserved on all copies. +.\" +.\" Permission is granted to copy and distribute modified versions of this +.\" manual under the conditions for verbatim copying, provided that the +.\" entire resulting derived work is distributed under the terms of a +.\" permission notice identical to this one. +.\" +.\" Since the Linux kernel and libraries are constantly changing, this +.\" manual page may be incorrect or out-of-date. The author(s) assume no +.\" responsibility for errors or omissions, or for damages resulting from +.\" the use of the information contained herein. The author(s) may not +.\" have taken the same level of care in the production of this manual, +.\" which is licensed free of charge, as they might when working +.\" professionally. +.\" +.\" Formatted or processed versions of this manual, if unaccompanied by +.\" the source, must acknowledge the copyright and authors of this work. +.\" +.\" References consulted: +.\" Linux libc source code +.\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991) +.\" 386BSD man pages +.\" Modified Sun Mar 28 00:25:51 1993, David Metcalfe +.\" Modified Sat Jul 24 18:13:39 1993 by Rik Faith (faith@cs.unc.edu) +.\" Modified Sun Aug 20 21:47:07 2000, aeb +.\" +.TH RANDOM 3 2000-08-20 "GNU" "Linux Programmer's Manual" +.SH NAME +random, srandom, initstate, setstate \- random number generator +.SH SYNOPSIS +.nf +.B #include <stdlib.h> +.sp +.B long int random(void); +.nl +.BI "void srandom(unsigned int " seed ); +.nl +.BI "char *initstate(unsigned int " seed ", char *" state ", size_t " n ); +.nl +.BI "char *setstate(char *" state ); +.fi +.SH DESCRIPTION +The \fBrandom()\fP function uses a non-linear additive feedback random +number generator employing a default table of size 31 long integers to +return successive pseudo-random numbers in the range from 0 to \fBRAND_MAX\fR. +The period of this random number generator is very large, approximately +16*((2**31)\-1). +.PP +The \fBsrandom()\fP function sets its argument as the seed for a new +sequence of pseudo-random integers to be returned by \fBrandom()\fP. +These sequences are repeatable by calling \fBsrandom()\fP with the same +seed value. If no seed value is provided, the \fBrandom()\fP function +is automatically seeded with a value of 1. +.PP +The \fBinitstate()\fP function allows a state array \fIstate\fP to +be initialized for use by \fBrandom()\fP. The size of the state array +\fIn\fP is used by \fBinitstate()\fP to decide how sophisticated a +random number generator it should use \(em the larger the state array, +the better the random numbers will be. \fIseed\fP is the seed for the +initialization, which specifies a starting point for the random number +sequence, and provides for restarting at the same point. +.PP +The \fBsetstate()\fP function changes the state array used by the +\fBrandom()\fP function. The state array \fIstate\fP is used for +random number generation until the next call to \fBinitstate()\fP +or \fBsetstate()\fP. \fIstate\fP must first have been initialized +using \fBinitstate()\fP or be the result of a previous call of +\fBsetstate()\fP. +.SH "RETURN VALUE" +The \fBrandom()\fP function returns a value between 0 and RAND_MAX. +The \fBsrandom()\fP function returns no value. The \fBinitstate()\fP +and \fBsetstate()\fP functions return a pointer to the previous state +array, or NULL on error. +.SH ERRORS +.TP +.B EINVAL +A state array of less than 8 bytes was specified to \fBinitstate()\fP. +.SH NOTES +Current "optimal" values for the size of the state array \fIn\fP are +8, 32, 64, 128, and 256 bytes; other amounts will be rounded down to +the nearest known amount. Using less than 8 bytes will cause an +error. +.SH "CONFORMING TO" +BSD 4.3 +.SH "SEE ALSO" +.BR rand (3), +.BR srand (3) |