How to generate a random integer with specific range(for example, from 1 to 1000)?
Also, how to convert a floating point number into a integer? (2 Replies)
Hi...How can I generate random numbers between a given range ...preferably between 1 and 100...in UNIX C programming...?
I tried out functions like rand(),drand48() etc but didnt get satisfactory results...
Thanks a lot in advance.......... (1 Reply)
HI
please help me in solving this issue.
I have a shell script which consists of ten statemnts ( i mean 10 executable statments)...........and if i run that script the 10 statmenst will execute continously ............
But now my probelm is i have to write another script --> to... (0 Replies)
Dear all,
I get the situation from my office but i cannot think what is happening. please give me some advise.
1. some file owner and group is changed to a very long number
2. i login as root. when i touch a file or operate on the file like chown, cp, the response is "Read-only file system".... (1 Reply)
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)
I need to generate and reuse a 5 digit random number every time my program is executed. But the following generates random numbers every time the function is called.
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <string.h>
#include <time.h>
... (12 Replies)
I saw this formula to generate random number between two specified values in shell script.the following.
$(((RANDOM%(max-min+divisibleBy))/divisibleBy*divisibleBy+min))
Give a example in book.
Generate random number between 6 and 30.like this.
$(((RANDOM%30/3+1)*3))
But I have a... (1 Reply)
Hi,
I'm trying to create a script that will print random numbers with length of three.
Below is the expected out.
928-377-899
942-458-310
951-948-511
962-681-415
995-161-708
997-997-209
thanks (4 Replies)
How can I choose randomly the row numbers of my file in awk? (4 Replies)
Discussion started by: Homa
4 Replies
LEARN ABOUT REDHAT
urandom
RANDOM(4) Linux Programmer's Manual RANDOM(4)NAME
random, urandom - kernel random number source devices
DESCRIPTION
The character special files /dev/random and /dev/urandom (present since Linux 1.3.30) provide an interface to the kernel's random number
generator. File /dev/random has major device number 1 and minor device number 8. File /dev/urandom has major device number 1 and minor
device number 9.
The random number generator gathers environmental noise from device drivers and other sources into an entropy pool. The generator also
keeps an estimate of the number of bit of the noise in the entropy pool. From this entropy pool random numbers are created.
When read, the /dev/random device will only return random bytes within the estimated number of bits of noise in the entropy pool.
/dev/random should be suitable for uses that need very high quality randomness such as one-time pad or key generation. When the entropy
pool is empty, reads to /dev/random will block until additional environmental noise is gathered.
When read, /dev/urandom device will return as many bytes as are requested. As a result, if there is not sufficient entropy in the entropy
pool, the returned values are theoretically vulnerable to a cryptographic attack on the algorithms used by the driver. Knowledge of how to
do this is not available in the current non-classified literature, but it is theoretically possible that such an attack may exist. If this
is a concern in your application, use /dev/random instead.
CONFIGURING
If your system does not have /dev/random and /dev/urandom created already, they can be created with the following commands:
mknod -m 644 /dev/random c 1 8
mknod -m 644 /dev/urandom c 1 9
chown root:root /dev/random /dev/urandom
When a Linux system starts up without much operator interaction, the entropy pool may be in a fairly predictable state. This reduces the
actual amount of noise in the entropy pool below the estimate. In order to counteract this effect, it helps to carry entropy pool informa-
tion across shut-downs and start-ups. To do this, add the following lines to an appropriate script which is run during the Linux system
start-up sequence:
echo "Initializing kernel random number generator..."
# Initialize kernel random number generator with random seed
# from last shut-down (or start-up) to this start-up. Load and
# then save 512 bytes, which is the size of the entropy pool.
if [ -f /var/random-seed ]; then
cat /var/random-seed >/dev/urandom
fi
dd if=/dev/urandom of=/var/random-seed count=1
Also, add the following lines in an appropriate script which is run during the Linux system shutdown:
# Carry a random seed from shut-down to start-up for the random
# number generator. Save 512 bytes, which is the size of the
# random number generator's entropy pool.
echo "Saving random seed..."
dd if=/dev/urandom of=/var/random-seed count=1
FILES
/dev/random
/dev/urandom
AUTHOR
The kernel's random number generator was written by Theodore Ts'o (tytso@athena.mit.edu).
SEE ALSO
mknod (1)
RFC 1750, "Randomness Recommendations for Security"
Linux 1997-08-01 RANDOM(4)