[SOLVED] I need to generate random number either 1 or 0?

mvmacd · 01-21-2010, 04:02 PM

Not only that but I need tons and tons of them generated, and I need it to be totally random each time.

Code:

matthew@mvm:/h/misc> cat a
#!/bin/bash
for i in {1..5}; do
echo $RANDOM
done
matthew@mvm:/h/misc> ./a
17767
9158
6249
18547
23633
matthew@mvm:/h/misc> ./a
17767
9158
6249
18547
23633
matthew@mvm:/h/misc>

There you can see that it is the same number. It does that every time!! Grrr. The strange thing is each time I manually type [or copy & paste] it into the terminal, it gives random [not static, like I am getting from my script] results.

The reason I want this is because I am making a script where this line will randomly go up or down [depending on if the random number is 1 or 0]. Thanks, Matt

pixellany · 01-21-2010, 04:40 PM

I see 2 questions here:

1. Getting random numbers to be 0 or 1: try this:

Code:

echo $(($RANDOM%2))

2. Reseeding the random number generator: See here:
http://www.faqs.org/docs/bashman/bashref_60.html
scroll down to the entry for "RANDOM"

irmin · 01-21-2010, 04:43 PM

RANDOM will contain only pseudo random numbers. If you need real random numbers you should consider reading from /dev/random or /dev/urandom.

mvmacd · 01-21-2010, 05:06 PM

Quote:

Originally Posted by pixellany

I see 2 questions here:

1. Getting random numbers to be 0 or 1: try this:

Code:

echo $(($RANDOM%2))

2. Reseeding the random number generator: See here:
http://www.faqs.org/docs/bashman/bashref_60.html
scroll down to the entry for "RANDOM"

Still doesn't work:

Code:

matthew@mvm:/h/misc> cat numberr
#!/bin/bash
echo $RANDOM
RANDOM="1"
echo $RANDOM
matthew@mvm:/h/misc> ./numberr
24247
17767
matthew@mvm:/h/misc>

:Sigh: I don't really care if I use $RANDOM or /dev/random, just as long as it generates a 1 or 0 quickly! Because if there is a 1 the $num will go up, then it will dislpay $num number of "."s (Periods). So going quickly it will randomly go up, down, etc... How would I use /dev/random? Or how would I get the $RANDOM to reset each time before it is called?? Thanks

edit: Hm it looks like it did work....... But the only problem is the 2nd number always stays the same! :\ :?

mvmacd · 01-21-2010, 06:50 PM

thanks, I got it to work by:

get_number () {
RANDOM=""
rndm=$RANDOM
}