Test max open files limit, `ulimit -n` | Source: https://stackoverflow.com/a/68895690

test-open-files-limit.sh

#!/usr/bin/env bash
case $BASH_VERSION in
  ''|[1-3].*|4.0.*) echo "ERROR: Bash 4.1 or newer required" >&2; exit 1;;
esac

[[ $1 ]] || { echo "Usage: $0 number-of-files" >&2; exit 1; }

echo "Running as process $$" >&2
for ((i=0; i<$1; i++)); do
  exec {fd_num}>/dev/null || {
    echo "Error on iteration $((i+1))" >&2
    break
  }
done

# if started from a TTY, let user press enter to exit
if [[ -t 0 ]]; then
  read -p "Press enter to exit this process:" _
fi