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up vote 6 down vote favorite
1

In a program, I need to set a variable to a random value of either 0 or 1.

I can't figure out how to do it and Google has failed me.

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up vote 7 down vote

One easy method is to use $RANDOM to retrieve a pseudorandom 16 bit integer number in the range [0; 32767]. You can simply convert that to [0; 1] by calculating modulo 2 of the random number:

echo $(( $RANDOM % 2 ))

More information about Bash's $RANDOM: http://www.tldp.org/LDP/abs/html/randomvar.html

With that simple construct you can easily build powerful scripts using randomness, like in this comic...

Commit Strip - Russian Roulette

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up vote 6 down vote

You could use shuf

DESCRIPTION Write a random permutation of the input lines to standard output.

   -i, --input-range=LO-HI
          treat each number LO through HI as an input line
   -n, --head-count=COUNT
          output at most COUNT lines

$ foo=$(shuf -i0-1 -n1)
$ echo $foo
1
$ foo=$(shuf -i0-1 -n1)
$ echo $foo
0
$ foo=$(shuf -i0-1 -n1)
$ echo $foo
0
$ foo=$(shuf -i0-1 -n1)
$ echo $foo
1
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up vote 2 down vote

How about:

#!/bin/bash
r=$(($RANDOM % 2))
echo $r

Or even:

r=$(($(od -An -N1 -i /dev/random) % 2))
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up vote 0 down vote

The easiest way I found was to use shuf -i 0-1 -n 1as it genarates a random number in the range which is inclusive

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