Need to generate a file with random data. /dev/[u]random doesn't exist.

Thread Tools Search this Thread
Top Forums Shell Programming and Scripting Need to generate a file with random data. /dev/[u]random doesn't exist.
# 1  
Old 08-16-2013
Need to generate a file with random data. /dev/[u]random doesn't exist.

Need to use dd to generate a large file from a sample file of random data. This is because I don't have /dev/urandom.

I create a named pipe then:

dd if=mynamed.fifo do=myfile.fifo bs=1024 count=1024

but when I cat a file to the fifo that's 1024 random bytes:

cat randomfile.txt > mynamed.fifo;

the dd command exits writing only 1024 (Likely the EOF thing). so I never get my 1MB file. How do I get around this? How do I ensure it generates the random data file without closing dd? Is there something else I need to pass?


Last edited by Scott; 08-16-2013 at 01:05 PM.. Reason: Code tags, please.
# 2  
Old 08-16-2013
Why not just read/write the first 1MB from file(randomfile.txt) to another file:
head -c1MB randomfile.txt > test.txt

# 3  
Old 08-16-2013
What system doesn't have /dev/urandom? What languages do you have available?

How about this? When dd quits, it should kill the while-loop too. No named pipe needed.

while true
        cat inputfile
done | dd bs=1024 count=1024 > outputfile

# 4  
Old 08-19-2013
Could you use openssl to generate your random file directly, e.g. for 1Mb file use:

$ openssl rand 1048576 > myfile.fifo

This User Gave Thanks to Chubler_XL For This Post:
# 5  
Old 08-22-2013
Thanks very much all for the replies. Really appreciate it. The place to run this for me would be even in basic shells like the Linux, Solaris, AIX etc 'maintenance' / 'recovery' shells.

So things like Perl or openssl won't work as required libraries won't be loaded in those simple recovery shells.

That's a good option there but unfortunately it didn't work fully or I should say it DID work partially. The loop continued to run even though the dd command ended / stopped.


Last edited by Devyn; 08-22-2013 at 06:49 PM..
# 6  
Old 08-22-2013
How about just using dd to append to file each time:

$ dd if=randomfile1.txt of=myfile.fifo oflag=append conv=notrunc
$ dd if=randomfile2.txt of=myfile.fifo oflag=append conv=notrunc
$ dd if=randomfile1.txt of=myfile.fifo oflag=append conv=notrunc

# 7  
Old 08-22-2013
Thinking laterally, a long shot, but worth a try...

Not sure why you need to use 1024 for block size, but my dd command will accept a bs of 1048576 so...
dd if=mynamed.fifo of=myfile.fifo bs=1048576 count=1

Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. HP-UX

Dev/urandom and dev/random missing in 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. Shell Programming and Scripting

Help with generate a pair of random number

Hi, Is anybody experience generate a pair of random number by using awk command? I wanna to generate a pair of random number (range from 1 to 4124) and repeats it 416 times. Desired output 2 326 123 1256 341 14 3245 645 . . . I did write the below command: awk... (5 Replies)
Discussion started by: perl_beginner
5 Replies

3. Shell Programming and Scripting

Generate random numbers in script

i want to generate a random number through a script, and even if anyone reads the script, they wont be able to figure out what the random number is. only the person who setup the script would know it. something like this could work: random the full thread is here: ... (13 Replies)
Discussion started by: SkySmart
13 Replies

4. UNIX for Dummies Questions & Answers

how to generate random number as as the first column of a txt file

Dear all, I have a question. I have a txt file say 4000 rows X 1800 Column. I 'd like to creat a new column as the first column which is a column of random numbers (n=4000) thanks a lot! Lin (2 Replies)
Discussion started by: forevertl
2 Replies

5. Shell Programming and Scripting

generate random base 16

How would you use bash to generate a random 32 digit number base 16? Like this one: 0cc06f2fa0166913291afcb788717458 (8 Replies)
Discussion started by: locoroco
8 Replies

6. Programming

generate array of random numbers

hi guys, I am writing a c program that generates a two dimensional array to make matrix and a vector of random numbers and perform multiplication. I can't figure out whats wrong with my code. It generates a matrix of random numbers but all the numbers in the vector array is same and so is the... (2 Replies)
Discussion started by: saboture88
2 Replies

7. Programming

Generate random number

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 this. $(((RANDOM%30/3+1)*3)) But I have a... (1 Reply)
Discussion started by: luoluo
1 Replies

8. Programming

Generate Random Password in C

I need a function to generate a random alphanumeric password in C code. It needs to be between 6-8 characters and follow the following rules: Reject if same char appears # time: 4 or more Reject if same char appears consecutively: 3 or more I have the following random password working for... (2 Replies)
Discussion started by: vjaws
2 Replies

9. Shell Programming and Scripting

Generate a random password

Hello All... Can someone help me generate a random password which will be 7 characters long which contains alpha-numeric characters using shell script. I am looking to store the output of the script that generates the password to a variable within a script and use it as the password. ... (5 Replies)
Discussion started by: chiru_h
5 Replies

10. Programming

How to generate a random number?

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)
Discussion started by: MacMonster
2 Replies
Login or Register to Ask a Question

Featured Tech Videos