Bash/shell script: create four random-length strings with fixed total length - bash

Question

I would like to create four strings, each with a random length, but their total length should be 10. So possible length combinations could be:
3 3 3 1
or
4 0 2 2
Which would then (respectively) result in strings like this:
111 222 333 4
or
1111 33 44
How could I do this?

Answer 1

$RANDOM will give you a random integer in range 0..32767.
Using some arithmetic expansion you can do:
remaining=10
for i in {1..3}; do
next=$((RANDOM % remaining)) # get a number in range 0..$remaining
echo -n "$next "
((remaining -= next))
done
echo $remaining
Update: to repeat the number N times, you can use a function like this:
repeat() {
for ((i=0; i<$1; i++)); do
echo -n $1
done
echo
}
repeat 3
333

Answer 2

Here is an algorithm:
Make first 3 strings with random length, which is not greater than sum of lenght (each time substract it). And rest of length - it's your last string.
Consider this:
sumlen=10
for i in {1..3}
do
strlen=$(($RANDOM % $sumlen)); sumlen=$(($sumlen-$strlen)); echo $strlen
done
echo $sumlen
This will output your lengths, now you can create strings, suppose you know how

Answer 3

alternative awk solution
awk 'function r(n) {return int(n*rand())}
BEGIN{srand(); s=10;
for(i=1;i<=3;i++) {a=r(s); s-=a; print a}
print s}'
3
5
1
1
srand() to set a randomized seed, otherwise will generate the same random numbers each time.
Here you can combine the next task of generating the strings into the same awk script
$ awk 'function r(n) {return int(n*rand())};
function rep(n,t) {c="";for(i=1;i<=n;i++) c=c t; return c}
BEGIN{srand(); s=10;
for(j=1;j<=3;j++) {a=r(s); s-=a; printf("%s ", rep(a,j))}
printf("%s\n", rep(s,j))}'
generated
1111 2 3 4444