Generating random number between 1 and 10 in Bash Shell Script
To generate random numbers with bash use the $RANDOM internal Bash function. Note that $RANDOM should not be used to generate an encryption key. $RANDOM is generated by using your current process ID (PID) and the current time/date as defined by the number of seconds elapsed since 1970.
echo $RANDOM % 10 + 1 | bc
Simplest solution would be to use tool which allows you to directly specify ranges, like gnu shuf
shuf -i1-10 -n1
If you want to use $RANDOM
, it would be more precise to throw out the last 8 numbers in 0...32767, and just treat it as 0...32759, since taking 0...32767 mod 10 you get the following distribution
0-8 each: 3277
8-9 each: 3276
So, slightly slower but more precise would be
while :; do ran=$RANDOM; ((ran < 32760)) && echo $(((ran%10)+1)) && break; done
$(( ( RANDOM % 10 ) + 1 ))
EDIT. Changed brackets into parenthesis according to the comment. http://web.archive.org/web/20150206070451/http://islandlinux.org/howto/generate-random-numbers-bash-scripting
You can also use /dev/urandom:
grep -m1 -ao '[0-9]' /dev/urandom | sed s/0/10/ | head -n1