Does Linux and Mac OSX have built-in Credential/Password Managers with API access?

Does Linux and Mac OSX have built-in Credential/Password Managers with API access like Windows has with its CredMan (CredWrite, etc). It would be preferrable if they could be used without the need to have them installed.

Are there ones for Android and IOS?

Is Windows CredMan the best built-in choice to use on Windows XP and later to securely store credentials or even just strings?