10 More Discussions You Might Find Interesting
1. HP-UX
Hi,
In our HP-UX B.11.11. I could not find dev/urandom and dev/random
Are all pseudo-devices implemented as device drivers, or in need to run /configure some package to install the package to have dev/urandom.
Please help (4 Replies)
Discussion started by: rashi
4 Replies
2. UNIX for Advanced & Expert Users
Hi
I'm running the following command to generate a random password in a KSH script on a RHEL Linux VM but for some reason the cmd is not being closed and it's causing problems on the host.
PASSWORD="$(cat /dev/urandom | tr -dc "a-zA-Z0-9" | fold -w 16 | head -1)Aa0!"
The code worked as... (2 Replies)
Discussion started by: user052009
2 Replies
3. Shell Programming and Scripting
Hello,
I'm trying to send the error output of a 'cat' operation to /dev/null like this:
cat /dirA/dirB/temp*.log > /dirA/dirB/final.log 2>/dev/null
This works perfectly in a terminal, but not when placed in a script.
If there are no files matching temp*.log the script outputs an error... (7 Replies)
Discussion started by: Nils88
7 Replies
4. Slackware
I am having problems using soundes. Until a few moments ago
the following commands produced errors and no sound:
cat /usr/share/apps/kolf/sounds/blackhole.wav/ > /dev/dsp yielded:
/dev/dsp: Invalid argument
cat /usr/share/apps/kolf/sounds/blackhole.wav > /dev/audio yelded:
/dev/audio:... (3 Replies)
Discussion started by: slak0
3 Replies
5. Shell Programming and Scripting
I have a file with a single filename in it, which I want to assign to a BASH variable, so I've been trying:
c=$(head -1 somefile)
echo $c
which outputs correctly, but them when I do
...
somecommand $c
it says it can't find the file, is that because it's grabbing the whole line, and... (5 Replies)
Discussion started by: unclecameron
5 Replies
6. Shell Programming and Scripting
cat myname.txt
John Doe I
John Doe II
John Doe III
-----------------------------------------------------------------------
for i in `cat myname.txt`
do
echo This is my name: $i >> thi.is.my.name.txt
done
-----------------------------------------------------------------------
cat... (1 Reply)
Discussion started by: danimad
1 Replies
7. UNIX for Dummies Questions & Answers
Hi,
Excuse my ignorance here - I'm a networks man and my knowledge of all things unix is somewhat limited.
We have a very large file (/var/tmp/mond.log) that we need to zero - does the "cat /dev/null > /var/tmp/mond.log" command achieve this? (4 Replies)
Discussion started by: freakydancer
4 Replies
8. UNIX for Dummies Questions & Answers
Hi, how do I use /dev/urandom to generate a single number between 1-100? I can od /dev/urandom but it gives me an endless list of random numbers, I just want 1 between 1-100. How can I get that? Thanks. (12 Replies)
Discussion started by: Takumi
12 Replies
9. UNIX for Dummies Questions & Answers
I've a major file which includes other files and now I wanna 'cut' the file in several minor parts....like
....
find / -name "*.tmp" >filea
wc -l filea >fileb
sed -e '1s/ filea//' fileb >filec
AMOUNT=`cat filec`
if ; then
cat file a |head -100l (ell) |tail -100l >filec
cat file a |head... (6 Replies)
Discussion started by: svennie
6 Replies
10. Shell Programming and Scripting
hai
in my shell script i want to replace the following commands
1) more
2) head
3) tail
i want to try all type of possible options avaliabul in the above commands
please help in implementing those commands (9 Replies)
Discussion started by: g_s_r_c
9 Replies
random(7D) Devices random(7D)
NAME
random, urandom - Strong random number generator device
SYNOPSIS
/dev/random
/dev/urandom
DESCRIPTION
The /dev/random and /dev/urandom files are special files that are a source for random bytes generated by the kernel random number generator
device. The /dev/random and /dev/urandom files are suitable for applications requiring high quality random numbers for cryptographic pur-
poses.
The generator device produces random numbers from data and devices available to the kernel and estimates the amount of randomness (or
"entropy") collected from these sources. The entropy level determines the amount of high quality random numbers that are produced at a
given time.
Applications retrieve random bytes by reading /dev/random or /dev/urandom. The /dev/random interface returns random bytes only when suffi-
cient amount of entropy has been collected. If there is no entropy to produce the requested number of bytes, /dev/random blocks until more
entropy can be obtained. Non-blocking I/O mode can be used to disable the blocking behavior. The /dev/random interface also supports
poll(2). Note that using poll(2) will not increase the speed at which random numbers can be read.
Bytes retrieved from /dev/random provide the highest quality random numbers produced by the generator, and can be used to generate long
term keys and other high value keying material.
The /dev/urandom interface returns bytes regardless of the amount of entropy available. It does not block on a read request due to lack of
entropy. While bytes produced by the /dev/urandom interface are of lower quality than bytes produced by /dev/random, they are nonetheless
suitable for less demanding and shorter term cryptographic uses such as short term session keys, paddings, and challenge strings.
Data can be written to /dev/random and /dev/urandom. Data written to either special file is added to the generator's internal state. Data
that is difficult to predict by other users may contribute randomness to the generator state and help improve the quality of future gener-
ated random numbers.
By default, write access is restricted to the super-user. An administrator may change the default read/write restriction by changing the
permissions on the appropriate special files.
/dev/random collects entropy from providers that are registered with the kernel-level cryptographic framework and implement random number
generation routines. The cryptoadm(1M) utility allows an administrator to configure which providers will be used with /dev/random.
ERRORS
EAGAIN O_NDELAY or O_NONBLOCK was set and no random bytes are available for reading from /dev/random.
EINTR A signal was caught while reading and no data was transferred.
ENOXIO open(2) request failed on /dev/random because no entropy provider is available.
FILES
/dev/random
/dev/urandom
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Availability | SUNWcsr |
+-----------------------------+-----------------------------+
|Interface Stability |Evolving |
+-----------------------------+-----------------------------+
SEE ALSO
cryptoadm(1M), open(2), poll(2), attributes(5)
NOTES
/dev/random can be configured to use only the hardware-based providers registered with the kernel-level cryptographic framework by dis-
abling the software-based provider using cryptoadm(1M). You can also use cryptoadm(1M) to obtain the name of the software-based provider.
Because no entropy is available, disabling all randomness providers causes read(2) and poll(2) on /dev/random to block indefinitely and
results in a warning message being logged and displayed on the system console. However, read(2) and poll(2) on /dev/random continue to work
in this case.
An implementation of the /dev/random and /dev/urandom kernel-based random number generator first appeared in Linux 1.3.30.
A /dev/random interface for Solaris first appeared as part of the CryptoRand implementation.
SunOS 5.10 21 June 2004 random(7D)