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1 | .\" Copyright 2008 Michael Kerrisk <mtk.manpages@gmail.com> |
2 | .\" | |
3 | .\" Permission is granted to make and distribute verbatim copies of this | |
4 | .\" manual provided the copyright notice and this permission notice are | |
5 | .\" preserved on all copies. | |
6 | .\" | |
7 | .\" Permission is granted to copy and distribute modified versions of this | |
8 | .\" manual under the conditions for verbatim copying, provided that the | |
9 | .\" entire resulting derived work is distributed under the terms of a | |
10 | .\" permission notice identical to this one. | |
11 | .\" | |
12 | .\" Since the Linux kernel and libraries are constantly changing, this | |
13 | .\" manual page may be incorrect or out-of-date. The author(s) assume no | |
14 | .\" responsibility for errors or omissions, or for damages resulting from | |
15 | .\" the use of the information contained herein. The author(s) may not | |
16 | .\" have taken the same level of care in the production of this manual, | |
17 | .\" which is licensed free of charge, as they might when working | |
18 | .\" professionally. | |
19 | .\" | |
20 | .\" Formatted or processed versions of this manual, if unaccompanied by | |
21 | .\" the source, must acknowledge the copyright and authors of this work. | |
22 | .\" | |
23 | .\" | |
24 | .TH RANDOM_R 3 2008-03-07 "GNU" "Linux Programmer's Manual" | |
25 | .SH NAME | |
b75101c3 | 26 | random_r, srandom_r, initstate_r, setstate_r \- reentrant |
ceb141cf | 27 | random number generator |
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28 | .SH SYNOPSIS |
29 | .nf | |
30 | .B #include <stdlib.h> | |
31 | .sp | |
32 | .BI "int random_r(struct random_data *" buf ", int32_t *" result ); | |
33 | ||
34 | .BI "int srandom_r(unsigned int " seed ", struct random_data *" buf ); | |
35 | ||
36 | .BI "int initstate_r(unsigned int " seed ", char *" statebuf , | |
37 | .BI " size_t " statelen ", struct random_data *" buf ); | |
38 | .br | |
39 | .BI "int setstate_r(char *" statebuf ", struct random_data *" buf ); | |
40 | .fi | |
41 | .sp | |
42 | .in -4n | |
43 | Feature Test Macro Requirements for glibc (see | |
44 | .BR feature_test_macros (7)): | |
45 | .in | |
46 | .sp | |
47 | .ad l | |
48 | .BR random_r (), | |
49 | .BR srandom_r (), | |
50 | .BR initstate_r (), | |
51 | .BR setstate_r (): | |
52 | _SVID_SOURCE || _BSD_SOURCE | |
53 | .ad b | |
54 | .SH DESCRIPTION | |
55 | These functions are the reentrant equivalents | |
56 | of the functions described in | |
57 | .BR random (3). | |
58 | They are suitable for use in multithreaded programs where each thread | |
59 | needs to obtain an independent, reproducible sequence of random numbers. | |
60 | ||
61 | The | |
62 | .BR random_r () | |
63 | function is like | |
64 | .BR random (3), | |
65 | except that instead of using state information maintained | |
66 | in a global variable, | |
67 | it uses the state information in the argument pointed to by | |
68 | .IR buf . | |
69 | The generated random number is returned in the argument | |
70 | .IR result . | |
71 | ||
72 | The | |
73 | .BR srandom_r () | |
74 | function is like | |
75 | .BR srandom (3), | |
76 | except that it initializes the seed for the random number generator | |
77 | whose state is maintained in the object pointed to by | |
78 | .IR buf , | |
79 | instead of the seed associated with the global state variable. | |
80 | ||
81 | The | |
82 | .BR initstate_r () | |
83 | function is like | |
84 | .BR initstate (3) | |
85 | except that it initializes the state in the object pointed to by | |
86 | .IR buf , | |
87 | rather than initializing the global state variable. | |
88 | ||
89 | The | |
90 | .BR setstate_r () | |
91 | function is like | |
92 | .BR setstate (3) | |
93 | except that it modifies the state in the object pointer to by | |
94 | .IR buf , | |
95 | rather than modifying the global state variable. | |
96 | .SH "RETURN VALUE" | |
97 | All of these functions return 0 on success, or \-1 on error. | |
98 | .SH ERRORS | |
99 | .TP | |
100 | .B EINVAL | |
101 | A state array of less than 8 bytes was specified to | |
102 | .BR initstate_r (). | |
103 | .TP | |
104 | .B EINVAL | |
105 | The | |
106 | .I statebuf | |
107 | or | |
108 | .I buf | |
109 | argument to | |
110 | .BR setstate_r () | |
111 | was NULL. | |
112 | .TP | |
113 | .B EINVAL | |
114 | The | |
115 | .I buf | |
116 | or | |
117 | .I result | |
118 | argument to | |
119 | .BR random_r () | |
120 | was NULL. | |
121 | .SH "CONFORMING TO" | |
c8f2dd47 | 122 | These functions are nonstandard glibc extensions. |
b75101c3 | 123 | .\" These functions appear to be on Tru64, but don't seem to be on |
ceb141cf MK |
124 | .\" Solaris, HP-UX, or FreeBSD. |
125 | .SH "SEE ALSO" | |
126 | .BR drand48 (3), | |
127 | .BR rand (3), | |
128 | .BR random (3) |