---
name: "memshuffle"
section: "3pub"
platform: "linux"
package: "publib-dev"
version: "0.40-4"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/memshuffle"
---

# memshuffle(3pub)

make an array be in random order

## NAME

memshuffle - make an array be in random order

## SYNOPSIS

```
#include <publib.h>
void *memshuffle(void *block, size_t elsize, size_t elnum);
```

## DESCRIPTION

*memshuffle* will move around the elements of an array in a random fashion.  It uses the standard library function [*rand*(3)](/rand/3.md) to get the pseudo-random numbers it needs.  The caller must set a suitable seed with [*srand*(3)](/srand/3.md).

## RETURN VALUE

*memshuffle* returns its first argument.

## EXAMPLE

To shuffle an integer array one might do the following.

```
int array[4] = { 1, 2, 3, 4 };
memshuffle(array, sizeof(array[0]), 4);
```

## BUGS

On many systems [*rand*(3)](/rand/3.md) is not of very good quality.  However, it is the only random number generator that can be assumed to exist. Making it possible for the caller to provide an alternate source of random numbers (e.g., via a function pointer) is perhaps too more trouble than its worth.  A better way would be for everyone to fix their *rand*'s.

## SEE ALSO

publib(3), memrev(3), [rand(3)](/rand/3.md), [srand(3)](/srand/3.md)

## AUTHOR

Lars Wirzenius (lars.wirzenius@helsinki.fi)