Shell Programming and Scripting

Hi folks

I'm coding on Ubuntu 9.04 standard shell.

I'm writing a script that needs to generate a random number at some point of its execution.

When I do

Code:

echo $RANDOM

as a command inside shell, I clearly get some randomly generated number

However when I do

Code:

i=`$RANDOM`
echo $i

or even

Code:

echo $RANDOM

as lines inside a shell script that I later run, I get nothing. Both options just give me a blank.

What am I doing wrong?

Try

Code:

i=$(echo $RANDOM)
echo $i

Guru.

No luck. Same output

Hi

RANDOM is not available in all shells. I know for sure it is there in ksh/sh,not there in csh/tcsh. Since its working on your prompt, try to run your script in the same shell as is your command line.

Guru.

RANDOM wasn't available in Bourne Shell.

Hey guys

So I've just moved to a new machine, and reinstalled Ubuntu 10.04 from scratch. I first tried

Code:

$ echo $RANDOM

in the shell. It works.
Then, when I tried the same command as a one line shell script called test.sh, and ran

Code:

$ sh test.sh

My output was a blank line.

So RANDOM is clearly available in this shell. Just that it doesn't work inside a script. Now what?

In Ubuntu sh is symlinked to dash.

Code:

d@DeCoBuntu:~$ ls  -ltrh /bin/sh
lrwxrwxrwx 1 root root 4 2010-05-26 02:41 /bin/sh -> dash
d@DeCoBuntu:~$ ^C

however, if you're just looking for some random numbers and letters, you can do this in pretty much any shell:

Code:

d@DeCoBuntu:~$ type rand
rand is a function
rand () 
{ 
    tr -dc _A-Z-a-z-0-9 < /dev/urandom | head -c$1;
    echo
}

Less efficient, but it'll get the job done.