Identifying the system package manager

Start with the accepted answer to this question: How can I get distribution name and version number in a simple shell script?. Then, decide which package manager you want to use based on the detected distribution.

Instead of identify binary programs, you should start from identify distributions,

Just give you few lines that works in bash scripting:

declare -A osInfo;
osInfo[/etc/redhat-release]=yum
osInfo[/etc/arch-release]=pacman
osInfo[/etc/gentoo-release]=emerge
osInfo[/etc/SuSE-release]=zypp
osInfo[/etc/debian_version]=apt-get

for f in ${!osInfo[@]}
do
    if [[ -f $f ]];then
        echo Package manager: ${osInfo[$f]}
    fi
done

Althrough these parts can't be trusted, but generally people won't do that.

I opted to go this route after reviewing the others. This came up for me when running many docker containers and needing curl / jq and not being able to rely on what was available from job to job.

script:
 - packagesNeeded='curl jq'
 - if [ -x "$(command -v apk)" ];       then sudo apk add --no-cache $packagesNeeded
 - elif [ -x "$(command -v apt-get)" ]; then sudo apt-get install $packagesNeeded
 - elif [ -x "$(command -v dnf)" ];     then sudo dnf install $packagesNeeded
 - elif [ -x "$(command -v zypper)" ];  then sudo zypper install $packagesNeeded
 - else echo "FAILED TO INSTALL PACKAGE: Package manager not found. You must manually install: $packagesNeeded">&2; fi

In pure bash:

packagesNeeded='curl jq'
if [ -x "$(command -v apk)" ];       then sudo apk add --no-cache $packagesNeeded
elif [ -x "$(command -v apt-get)" ]; then sudo apt-get install $packagesNeeded
elif [ -x "$(command -v dnf)" ];     then sudo dnf install $packagesNeeded
elif [ -x "$(command -v zypper)" ];  then sudo zypper install $packagesNeeded
else echo "FAILED TO INSTALL PACKAGE: Package manager not found. You must manually install: $packagesNeeded">&2; fi