.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\"
+.\" %%%LICENSE_START(VERBATIM)
.\" 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.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
+.\" %%%LICENSE_END
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.\" References consulted:
.\" Linux libc source code
.\" 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 2010-09-20 "GNU" "Linux Programmer's Manual"
+.TH RANDOM 3 2019-03-06 "GNU" "Linux Programmer's Manual"
.SH NAME
random, srandom, initstate, setstate \- random number generator
.SH SYNOPSIS
.nf
.B #include <stdlib.h>
-.sp
+.PP
.B long int random(void);
-
+.PP
.BI "void srandom(unsigned int " seed );
-
+.PP
.BI "char *initstate(unsigned int " seed ", char *" state ", size_t " n );
-.br
+.PP
.BI "char *setstate(char *" state );
.fi
-.sp
+.PP
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
-.sp
+.PP
.ad l
.BR random (),
.BR srandom (),
.BR initstate (),
.BR setstate ():
.RS 4
-_SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500 ||
-_XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
+_XOPEN_SOURCE\ >=\ 500
+.\" || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
+ || /* Glibc since 2.19: */ _DEFAULT_SOURCE
+ || /* Glibc versions <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE
.RE
.ad
.SH DESCRIPTION
to decide how sophisticated a
random number generator it should use\(emthe larger the state array,
the better the random numbers will be.
+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 results in an error.
\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.
.BR initstate ()
or be the result of a previous call of
.BR setstate ().
-.SH "RETURN VALUE"
+.SH RETURN VALUE
The
.BR random ()
function returns a value between 0 and
The
.BR srandom ()
function returns no value.
+.PP
The
.BR initstate ()
function returns a pointer to the previous state array.
-The
+On error,
+.I errno
+is set to indicate the cause.
+.PP
+On success,
.BR setstate ()
-function returns a pointer to the previous state array, or NULL on error.
+returns a pointer to the previous state array.
+On error, it returns NULL, with
+.I errno
+set to indicate the cause of the error.
.SH ERRORS
.TP
.B EINVAL
+The
+.I state
+argument given to
+.BR setstate ()
+was NULL.
+.TP
+.B EINVAL
A state array of less than 8 bytes was specified to
.BR initstate ().
-.SH "CONFORMING TO"
-4.3BSD, POSIX.1-2001.
+.SH ATTRIBUTES
+For an explanation of the terms used in this section, see
+.BR attributes (7).
+.TS
+allbox;
+lbw23 lb lb
+l l l.
+Interface Attribute Value
+T{
+.BR random (),
+.BR srandom (),
+.br
+.BR initstate (),
+.BR setstate ()
+T} Thread safety MT-Safe
+.TE
+.SH CONFORMING TO
+POSIX.1-2001, POSIX.1-2008, 4.3BSD.
.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.
-.PP
-This function should not be used in cases where multiple threads use
+The
.BR random ()
-and the behavior should be reproducible.
+function should not be used in multithreaded programs
+where reproducible behavior is required.
Use
.BR random_r (3)
for that purpose.
.PP
Random-number generation is a complex topic.
.I Numerical Recipes in C: The Art of Scientific Computing
-(William H. Press, Brian P. Flannery, Saul A. Teukolsky, William
-T. Vetterling; New York: Cambridge University Press, 2007, 3rd ed.)
+(William H.\& Press, Brian P.\& Flannery, Saul A.\& Teukolsky, William
+T.\& Vetterling; New York: Cambridge University Press, 2007, 3rd ed.)
provides an excellent discussion of practical random-number generation
issues in Chapter 7 (Random Numbers).
.PP
For a more theoretical discussion which also covers many practical issues
-in depth, see Chapter 3 (Random Numbers) in Donald E. Knuth's
+in depth, see Chapter 3 (Random Numbers) in Donald E.\& Knuth's
.IR "The Art of Computer Programming" ,
volume 2 (Seminumerical Algorithms), 2nd ed.; Reading, Massachusetts:
Addison-Wesley Publishing Company, 1981.
-.SH "SEE ALSO"
+.SH BUGS
+According to POSIX,
+.BR initstate ()
+should return NULL on error.
+In the glibc implementation,
+.I errno
+is (as specified) set on error, but the function does not return NULL.
+.\" http://sourceware.org/bugzilla/show_bug.cgi?id=15380
+.SH SEE ALSO
+.BR getrandom (2),
.BR drand48 (3),
.BR rand (3),
.BR random_r (3),