detect_shell and package manager.

#!/bin/sh

# Detect the shell
if [ -n "$BASH_VERSION" ]; then
    SHELL_NAME="bash"
elif [ -n "$ZSH_VERSION" ]; then
    SHELL_NAME="zsh"
else
    SHELL_NAME="unknown"
fi

# Detect the package manager

case "$SHELL_NAME" in
    "bash" | "zsh")
        if command -v pkg &> /dev/null; then
            echo "FreeBSD system using pkg"
        elif command -v apt-get &> /dev/null; then
            echo "Debian-based system using apt-get"
        elif command -v yum &> /dev/null; then
            echo "Red Hat-based system using yum"
        elif command -v dnf &> /dev/null; then
            echo "Red Hat-based system using dnf"
        else
            echo "Unsupported or unknown package manager"
        fi
        ;;
    *)
        echo "Unsupported shell: $SHELL_NAME"
        ;;
esac