Hi Guys
i have a script that have variable called :
NIO=4
and i want the random function to own that variable inside it such as below :
D=$(cat /dev/urandom | tr -dc '0-$NIO' | fold -w 1 | head -n 1)

as u see i want to set range from 0-4
but i dont want to set 4
i want to set it as variable


the problem here is the random function dont understand the syntax above


hope to help me

cheers

The $RANDOM variable in bash generates a pseudo random number every time it is referenced. You could use modulo to force the number to always be between 0 and 4.

0-4 excluding 4. Use 5 instead if you want to include 4. If you want to use NIO to specify the max number like in your original post you could do:

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thansk , but im forced to work on the scenario above as the fourmaula above :
i have
D=$(cat /dev/urandom | tr -dc '0-4' | fold -w 1 | head -n 1)

wnt to replace it with
D=$(cat /dev/urandom | tr -dc '0-$NIO' | fold -w 1 | head -n 1)

can u hep me ?

I updated my original post. It has the correct equation.

Why are you "forced" to work with that "specific scenario"? Project constraints don't normally require a specific answer but to solve a problem. The answer I gave you does what you want in a simpler manner: generate a number between 0-4.

Single and double quotes have special meaning in bash. See "Quoting" section of the bash man page. tr -dc '0-$NIO' has single quites so it is using the literal characters $NIO instead of what you probably want (it to be interpreted as an environment variable). Use double quotes instead.

What are you actually trying to accomplish? What's then end goal? The real problem you're trying to solve?

1 members found this post helpful.

im really appreciating ur time so so so much .
i have already a script with long lines that i dont want to change .

i tried ur soltution , but it didnt work .
see below :
NIO="$(( $RANDOM % 4 ))"
[root@testvmpackagevpn ~]# D=$(cat /dev/urandom | tr -dc '0-$NIO' | fold -w 1 | head -n 1)
tr: range-endpoints of `0-$' are in reverse collating sequence order

as u see the NIO value is not recognized as we need

?!

No, replace D. See my original post again. You're still using single quotes.

Read the bash man page on Quoting, RANDOM environment variable, and Arithmetic Expansion to better understand my solution.

Also, if you're afraid to lose changes when changing your script consider using git version control. It tracks history as you change scripts.

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try this.

1 members found this post helpful.

Cat abuse alert.

1 members found this post helpful.

Hi Guys

you were both nice

the issue is resolved and that u so so so much


my best regards

please share your solution.
others will benefit.

ps:
cat abuse?

from the Artist formerly known as "The useless use of cat"