If all you care about is killing it, you don't need to eval the output. The output just unsets two environment variables which only matters in the current shell

If all you care about is killing it, you don't need to eval the output. The output just unsets two environment variables which only matters in the current shell context. $ ssh-agent SSH_AUTH_SOCK=/var/folders/8p/_pwq997168s7vdwwdg_qr1j40000gn/T//ssh-DE0IoJfU5rrM/agent.15015; export SSH_AUTH_SOCK; SSH_AGENT_PID=15016; export SSH_AGENT_PID; echo Agent pid 15016; $ SSH_AGENT_PID=15016; export SSH_AGENT_PID; $ ssh-agent -k unset SSH_AUTH_SOCK; unset SSH_AGENT_PID; echo Agent pid 15016 killed; That said, it doesn't hurt to eval it, so I overstated my case in my original comment.