Difference between revisions of "Dev random"
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| − | = Summary = | + | == Summary == |
| − | /dev/random and /dev/urandom are two Unix and *nix based devices that | + | /dev/random and /dev/urandom are two Unix and *nix based devices that process memory, disc, network dumps from the kernel. This allows us to use a "random" like seed for performing "random" tasks with the "random" function. |
| − | The difference between /dev/random and /dev/urandom is the | + | The difference between /dev/random and /dev/urandom is whether the device is "blocking" or "non blocking": |
| − | While /dev/random gives random seeds, it will wait until it | + | * While /dev/random gives random seeds, it will wait until it has something to give us, before returning the seed. |
| − | /dev/urandom does not stop us from when we do not have a new seed from dump, and will return also | + | * /dev/urandom does not stop us from when we do not have a new seed from dump, and will return also data that are less random. This way we will not need to wait until any type of activity will occur, but randomness is reduced. |
| − | = Coding = | + | == Coding == |
| − | In order to make Free Pascal work with /dev/random and /dev/random we | + | In order to make Free Pascal work with /dev/random and /dev/random we can write the following code: |
| + | <syntaxhighlight> | ||
| + | procedure RandomSeed; | ||
| + | var | ||
| + | f : file of integer; | ||
| + | i : integer; | ||
| − | + | begin | |
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
i := 0; | i := 0; | ||
filemode := 0; | filemode := 0; | ||
| Line 24: | Line 24: | ||
CloseFile (f); | CloseFile (f); | ||
RandSeed := i; | RandSeed := i; | ||
| − | + | end; | |
| + | </syntaxhighlight> | ||
| − | = Explanation = | + | == Explanation == |
| − | Like everything else in *nix like | + | Like everything else in *nix like OSes, everything is a file! So, we access urandom as a file and we read only one integer at a time. |
| − | Then, we place the data we made as RandSeed (the seed number that the function random uses). And that's it, we have a random seeder for | + | Then, we place the data we made as RandSeed (the seed number that the function random uses). And that's it, we have a random seeder for "random" usage. |
[[Category:Statistical algorithms]] | [[Category:Statistical algorithms]] | ||
| + | [[Category:Unix]] | ||
Revision as of 10:04, 22 April 2013
Summary
/dev/random and /dev/urandom are two Unix and *nix based devices that process memory, disc, network dumps from the kernel. This allows us to use a "random" like seed for performing "random" tasks with the "random" function.
The difference between /dev/random and /dev/urandom is whether the device is "blocking" or "non blocking":
- While /dev/random gives random seeds, it will wait until it has something to give us, before returning the seed.
- /dev/urandom does not stop us from when we do not have a new seed from dump, and will return also data that are less random. This way we will not need to wait until any type of activity will occur, but randomness is reduced.
Coding
In order to make Free Pascal work with /dev/random and /dev/random we can write the following code:
procedure RandomSeed;
var
f : file of integer;
i : integer;
begin
i := 0;
filemode := 0;
AssignFile(f, '/dev/urandom');
reset (f,1);
read (f,i);
CloseFile (f);
RandSeed := i;
end;Explanation
Like everything else in *nix like OSes, everything is a file! So, we access urandom as a file and we read only one integer at a time.
Then, we place the data we made as RandSeed (the seed number that the function random uses). And that's it, we have a random seeder for "random" usage.
