docs/docs/3.1/cmds/random.html
randomrandom SEEDrandom START ENDrandom START STEP ENDrandom choice [ITEMS...]
RANDOM generates a pseudo-random integer from a uniform distribution. The range (inclusive) is dependent on the arguments passed. No arguments indicate a range of [0; 32767]. If one argument is specified, the internal engine will be seeded with the argument for future invocations of RANDOM and no output will be produced. Two arguments indicate a range of [START; END]. Three arguments indicate a range of [START; END] with a spacing of STEP between possible outputs. RANDOM choice will select one random item from the succeeding arguments.
Note that seeding the engine will NOT give the same result across different systems.
You should not consider RANDOM cryptographically secure, or even statistically accurate.
The following code will count down from a random even number between 10 and 20 to 1:
for i in (seq (random 10 2 20) -1 1)echo $iend
And this will open a random picture from any of the subdirectories:
open (random choice \*\*jpg)