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Random elements from array

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# 1  
Old 02-26-2016
Random elements from array
Hi
I wanted to print random elements from an array at bash shell
I use the following code, but I always see first element getting printed
Code:
#!/bin/bash
c=1
expressions=(pink red white yellow purple)
while [[ $c -le 9 ]]; do
echo "The value of RANDOM is $RANDOM"
selectedexpression=${expressions[$RANDOM % ${#RANDOM[*]}]};
echo "***** The option is $selectedexpression"
sleep 1
((c++))
 done

The output as follows:
Code:
The value of RANDOM is 10813
***** The option is pink
The value of RANDOM is 30688
***** The option is pink
The value of RANDOM is 9752
***** The option is pink
The value of RANDOM is 2170
***** The option is pink
The value of RANDOM is 4010
***** The option is pink
The value of RANDOM is 31161
***** The option is pink
The value of RANDOM is 2046
***** The option is pink
The value of RANDOM is 5365
***** The option is pink
The value of RANDOM is 26738
***** The option is pink

I tried changing the sleep values till 7 but still only first element gets printed..
Please helpSmilie
# 2  
Old 02-26-2016
Hi.

For ${#RANDOM[*]}, where do you define array RANDOM?

Best wishes ... cheers, drl
# 3  
Old 02-26-2016
Is it possible your intention was sth like
Code:
selectedexpression=${expressions[$RANDOM % ${#expressions[*]}]}

?
# 4  
Old 02-26-2016
Since your modifiying the $RANDOM with the length(count) of its array items, and since $RANDOM has only one, only the first items is displayed.

Hope this helps
# 5  
Old 02-26-2016
I have used date command to seed random value
Code:
#!/bin/bash
c=1
RANDOM=$$$(date +%s)
expressions=(pink red white yellow purple)
while [[ $c -le 9 ]]; do
echo "The value of RANDOM is $RANDOM"
selectedexpression=${expressions[$RANDOM % ${#RANDOM[*]}]};
echo "***** The option is $selectedexpression"
sleep 1
((c++))
 done

# 6  
Old 02-26-2016
Hi Priya,
You still need to change:
Code:
selectedexpression=${expressions[$RANDOM % ${#RANDOM[*]}]};

to:
Code:
selectedexpression=${expressions[$RANDOM % ${#expressions[*]}]};

And, note that $RANDOM is reevaluated each time it is expanded. So the value printed by:
Code:
echo "The value of RANDOM is $RANDOM"

and the value used in:
Code:
selectedexpression=${expressions[$RANDOM % ${#expressions[*]}]};

have a VERY small chance of being the same value. If you want to print and use the same pseudo-random number, you need something more like:
Code:
rn="$RANDOM"
echo "The value of RANDOM is $rn"
selectedexpression=${expressions[$rn % ${#expressions[*]}]};

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