On Wed, Oct 21, 2026 at 20:30:25 +0200, Franco Martelli wrote: > First of all thanks Greg for your patience explaining me coding. I'm > interested about avoid to call an external tool inside the loop, do you have > a snippet of code that provides random numbers in a specified range using a > bash function?
https://mywiki.wooledge.org/BashFAQ/026 > You talked me about a Bash function able to return a random value between 1 > and n, at page #107 of the ABS I see that I have to use the 'modulo' > operator to apply a range to a variable assigned with $RANDOM but it doesn't > explain how to start from 1 and not from 0. Do I have to accept ranges from > 0 to n and then discard the 0? Well, usually you want 0 to n-1 because arrays are indexed from 0. If you want 1 to n, you can use something that gives you 0 to n-1, and then add 1 to it. Given an array of n elements, if we first store the size in a variable for convenience: n=${#array[@]} then the *easiest* way to select a random element (0 to n-1) is to use: ${array[RANDOM % n]} But as FAQ 26 explains, this is imperfect. There is a bias toward the lower numbers (unless n is an exact divisor of 32768). So, you have to decide whether you can live with that bias or not. For something that's just generating a playlist of songs, this may be good enough. Otherwise, you can use a function like this one from FAQ 26: rand() { local max=$((32768 / $1 * $1)) while (( (r=RANDOM) >= max )); do :; done r=$(( r % $1 )) } You'd use it like this: clips=(...) n=${#clips[@]} declare -A chosen playlist=() for i in {1..10}; do # Get an unused clip, which may take several tries. while true; do rand "$n" # Get a clip index number in global variable r. [[ ${chosen[$r]} ]] && continue # If we get to this point, it's a new one. chosen[r]=1 playlist+=( "${clips[r]}" ) break done done That generates a "playlist" array with 10 randomly selected, unique elements from the "clips" array. I didn't add any sanity checking, so there are some obvious issues, like an infinite loop if clips has fewer than 10 elements. But it should be a decent starting point. Another algorithm for solving this same problem would be to randomly shuffle the clips array, and then use the first 10 elements as your playlist. I won't include code for that, but you should be able to do that using the examples in FAQ 26.
