diff options
| author | Alejandro Colomar <alx@kernel.org> | 2023-01-01 17:18:22 +0100 |
|---|---|---|
| committer | Alejandro Colomar <alx@kernel.org> | 2023-01-01 17:49:31 +0100 |
| commit | 848404feb5bfbdcb9b8f693ec29159231ee2a7c8 (patch) | |
| tree | 445c2f76329cb2647073ccb8831c63bd0881ede0 | |
| parent | ca48829aad6801796d212c61add23e4a885786c7 (diff) | |
| download | man-pages-848404feb5bfbdcb9b8f693ec29159231ee2a7c8.tar.gz | |
arc4random.3: New page documenting the arc4random(3) family of functions
arc4random(3)
arc4random_uniform(3)
arc4random_buf(3)
Signed-off-by: Alejandro Colomar <alx@kernel.org>
| -rw-r--r-- | man3/arc4random.3 | 104 |
1 files changed, 104 insertions, 0 deletions
diff --git a/man3/arc4random.3 b/man3/arc4random.3 new file mode 100644 index 0000000000..2afcec2c4e --- /dev/null +++ b/man3/arc4random.3 @@ -0,0 +1,104 @@ +.\" Copyright (C) 2023 Alejandro Colomar <alx@kernel.org> +.\" +.\" SPDX-License-Identifier: Linux-man-pages-copyleft +.\" +.TH arc4random 3 (date) "Linux man-pages (unreleased)" +.SH NAME +arc4random, arc4random_uniform, arc4random_buf +\- cryptographically-secure pseudorandom number generator +.SH LIBRARY +Standard C library +.RI ( libc ", " -lc ) +.SH SYNOPSIS +.nf +.B #include <stdlib.h> +.PP +.B uint32_t arc4random(void); +.BI "uint32_t arc4random_uniform(uint32_t " upper_bound ); +.BI "void arc4random_buf(void " buf [. n "], size_t " n ); +.fi +.SH DESCRIPTION +These functions give cryptographically-secure random numbers. +.PP +.BR arc4random () +returns a uniformly-distributed value. +.PP +.BR arc4random_uniform () +returns a uniformly-distributed value less than +.I upper_bound +(see CAVEATS). +.PP +.BR arc4random_buf () +fills the memory pointed to by +.IR buf , +with +.I n +bytes of random data. +.PP +The +.BR rand (3) +and +.BR drand48 (3) +families of functions should only be used where +the quality of the random numbers is not a concern +.I and +there's a need for repeatability of the results. +Unless you meet both of those conditions, +use the +.BR arc4random () +functions. +.SH RETURN VALUE +.BR arc4random () +returns a random number. +.PP +.BR arc4random_uniform () +returns a random number less than +.I upper_bound +for valid input, or +.B 0 +when +.I upper_bound +is invalid. +.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 arc4random (), +.BR arc4random_uniform (), +.BR arc4random_buf () +T} Thread safety MT-Safe +.TE +.hy +.ad +.sp 1 +.SH STANDARDS +These nonstandard functions are present on several Unix systems. +.SH CAVEATS +An +.I upper_bound +of +.B 0 +doesn't make sense in a call to +.BR arc4random_uniform (). +Such a call will fail, and return +.BR 0 . +Be careful, +since that value is +.I not +less than +.IR upper_bound . +In some cases, +such as accessing an array, +using that value could result in Undefined Behavior. +.SH SEE ALSO +.BR getrandom (3), +.BR rand (3), +.BR drand48 (3), +.BR random (7) |