port-dependents(1) Manual Page

port dependents reports which ports depend upon a given (installed) port, if any. Note that dependents does not work for ports that are not installed on your system. It uses the database of installed ports that MacPorts keeps internally, which records the dependency relations at installation time. port dependents prints this information.

For this reason, port dependents does not work for ports that are not installed on your system. If you want to find out which ports depend on a port you haven’t installed, you can use the depends: pseudo-portname selector:

This command will, however, not cover dependencies that are only present in non-default variants. For more information about pseudo-portname selectors, see port(1).

port rdependents will print a tree of installed ports that depend on the given port.

The dependency relations printed by port dependents and port rdependents are the same that are used to determine if a port can be safely uninstalled. Ports that still have dependents installed cannot be safely uninstalled without possibly breaking their dependents. All dependents can be removed at the same time using the --follow-dependents flag. The check can be ignored using the -f flag. See port-uninstall(1) for more details.

Do not confuse dependents and dependencies (or, shortened, deps). Refer to the following example to understand the difference:

portA depends on portB, i.e., portA needs portB to run. Because of that, portB is a dependency (or dep) of portA. After installing portA, portB has been automatically installed. At this point, portA has become a dependent of portB. You can only uninstall portB once all of its dependents (i.e., including portA) have been uninstalled.

port(1), port-echo(1), port-deps(1), port-uninstall(1)