Checks which package manager to use.

which-pkg-manager.sh

#!/bin/bash

declare -A pkgman
pgkman[apt]=$(which apt)
pkgman[yum]=$(which yum)
pkgman[pacman]=$(which pacman)

for i in "${!pkgman[@]}" # takes index of array
do
  # apt (debian, ubuntu, mint...)
  if which "${pgkman[$i]}"; then # checks if the value (output of which) is not null
    
    if [ "$i" = apt ]; then
      echo "This system is running apt."
    fi

    # rpm/yum (redhat, opensuse, fedora, centos...)
    if [ "$i" = yum ]; then
      echo "This system is running yum."
    fi

    # pacman (arch, manjaro...)
    if [ "$i" = pacman ]; then
      echo "This system is running pacman."
    fi
  fi
done