Easily switch between different SSH agents on mac, probably easy to adapt to any linux

.zshrc

function showAgent() {
    echo The current SSH agent is $(readlink ~/.ssh-agent-link)
}

function updateSshAgentSock() {
    NEWSOCK=$2
    if [ -z "$NEWSOCK" ]; then
        echo -n "No socket found for ${1}; not changing agents. "
        return 1
    elif [ ! -S "$NEWSOCK" ]; then
        echo -n "Socket ${NEWSOCK} is not a socket; not changing agents. "
    else
        ln -sfv "$NEWSOCK" ~/.ssh-agent-link
    fi
    showAgent
}

function usegpg() {
    if pgrep -x "gpg-agent" > /dev/null; then
        gpgconf --reload gpg-agent
    else
        gpgconf --launch gpg-agent
    fi
    NEWSOCK=$(gpgconf --list-dirs agent-ssh-socket)

    if [ -z "$NEWSOCK" ]; then
        NEWSOCK=$(lsof -c gpg-agent | grep "\.ssh" | awk '{print $8}')
    fi
    updateSshAgentSock "gpg-agent" "$NEWSOCK"
}
function useagent() {
    NEWSOCK=$(launchctl getenv SSH_AUTH_SOCK)
    if [ -z "$NEWSOCK" ]; then
        # Less efficient and brute force way to get agent
        NEWSOCK=$(lsof -c ssh-agent | grep Listeners | awk '{print $8}')
    fi
    updateSshAgentSock "ssh-agent" "$NEWSOCK"
}
function usesekey() {
    NEWSOCK=~/.sekey/ssh-agent.ssh
    updateSshAgentSock "sekey" "$NEWSOCK"
}
export SSH_AUTH_SOCK=~/.ssh-agent-link