Sponsored Content
Top Forums Programming generating 16 digit random number in C Post 302344635 by jim mcnamara on Monday 17th of August 2009 07:33:57 AM
Old 08-17-2009
There is a reason - most systems double datatype has 15 digits of precision.
see limits.h DBL_DIG

Try long double instead. I also thought you needed 16 digits, not a numeric datatype like double.

For example, suppose you get 0000000123456789 from /dev/urandom. If that becomes a numeric datatype it no longer has 16 digits. It has only nine digits.
 

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

generating random numbers with hamming distance 4

Hi I want to genrate 10 random 32 bit binary numbers with hamming distance 4 and 8. 11010110010101010101010101010101 11010110010101010100010101010010 if we look carefully at these two binary numbers they differ at 4 places hence hamming distance 4. Now I want to genrate these numbers... (2 Replies)
Discussion started by: hack_tom
2 Replies

2. Shell Programming and Scripting

Generating random number within a specific range (0.5-1.5)

Hello, need a way to generate numbers within 0.5-1.5 range Has to be totally random: 0.6 1.1 0.8 1.5 0.6 and so on.... How to? (10 Replies)
Discussion started by: TehOne
10 Replies

3. Shell Programming and Scripting

Generating random numbers

Hi, I am having trouble with generating random numbers. can this be done with awk? So I have a file that looks like this: 23 30 24 40 26 34 So column1 is start and column2 is end. I want to generate 3 random #'s between start and stop: So the output will look like this: ... (9 Replies)
Discussion started by: phil_heath
9 Replies

4. Programming

C Help; generating a random number.

Im new to C, and Im having a hard time getting a random number. In bash, I would do something similar to the following to get a random number; #!/bin/bash seed1=$RANDOM seed2=$RANDOM seed3=$RANDOM SEED=`expr $seed1 * $seed2 / $seed3` echo ${SEED%.*} Now, in online examples... (4 Replies)
Discussion started by: trey85stang
4 Replies

5. Programming

Generating Random Number in Child Process using Fork

Hello All, I am stuck up in a program where the rand functions ends up giving all the same integers. Tried sleep, but the numbers turned out to be same... Can anyone help me out how to fix this issue ? I have called the srand once in the program, but I feel like when I call fork the child process... (5 Replies)
Discussion started by: manisum
5 Replies

6. Shell Programming and Scripting

Generate 16 digit positive random Numbers

Hi Unix Gurus, I have a requirement to generate positive random 16 and 13 digit numbers. Here is the script I have so far..... number=$RANDOM$RANDOM$RANDOM$RANDOM; let "number %= 10000000000000"; echo $number But sometimes it is generating negative numbers and also 15 digit... (8 Replies)
Discussion started by: scorpioraghu
8 Replies

7. Shell Programming and Scripting

Generating Random Number in certain range

Hi there I am trying to generate a random number between 40 and 70 using the shell here is my code so far and it keeps going above 70. all help much appreciated! comp=$(( RANDOM%70+40 )) echo $comp (4 Replies)
Discussion started by: faintingquiche
4 Replies

8. Shell Programming and Scripting

Random number generating script?

Having a hard time with this. Very new to scripting and linux. Spent all sunday trying to do this. Appreciate some help and maybe help breaking down what the syntax does. Create a Bash program. It should have the following properties • Creates a secret number between 1 and 100 i. The... (3 Replies)
Discussion started by: LINUXnoob15
3 Replies

9. Shell Programming and Scripting

Generating a Random String of 'n' length

Hi, How can I generate a string of random characters (alpha+numeric) of a particular length ? For e.g. for n=5, output = 'kasjf' n=10, output = 'hedbcd902k' Also, please let me know if random (valid) dates could also be generated. Thanks (7 Replies)
Discussion started by: rishigc
7 Replies

10. Shell Programming and Scripting

Generating a POSIX random number?

Hi Guys and gals... As you know I am getting to grips with POSIX and hit this stumbling block. Generating two random numbers 0 to 255 POSIXly. Speed in not important hence the 'sleep 1' command. I have done a demo that works, but it sure is ugly! Is there a better way? #!/bin/sh # Random... (12 Replies)
Discussion started by: wisecracker
12 Replies
rand(3C)																  rand(3C)

NAME
rand(), rand_r(), srand() - simple random-number generator SYNOPSIS
DESCRIPTION
uses a multiplicative, congruential, random-number generator with period 2^32 that returns successive pseudo-random numbers in the range from 0 to 2^15-1. can be called at any time to reset the random-number generator to a random starting point. The generator is initially seeded with a value of 1. returns a random number at the address pointed to by the randval parameter. The seed parameter can be set at any time to start the random- number generator at an arbitrary point. Note The spectral properties of leave a great deal to be desired. provides a much better, though more elaborate, random-number generator (see drand48(3C)). RETURN VALUE
If seed or randval is NULL, returns 0. Otherwise, returns a psuedo-random integer. EXAMPLES
The following: int x, y; srand(10); x = rand(); y = rand(); would produce the same results as: int x, y, s = 10; x=rand_r(&s); y=rand_r(&s); WARNINGS
Users of should note that rand_r() now conforms with POSIX.1c. The old prototype of is supported for compatibility with existing DCE applications only. SEE ALSO
drand48(3C), random(3M), thread_safety(5), random(7). STANDARDS CONFORMANCE
rand(3C)

Featured Tech Videos

All times are GMT -4. The time now is 06:12 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy