¿Cómo puedo compartir un archivo en el mismo host de MacOS?

Debería haber buscado en Google primero :-[[

https://support.apple.com/en-by/guide/mac-help/mh17131/mac

Para citar:

Set up file sharing
On your Mac, choose Apple menu  > System Preferences, then click Sharing .
Select the File Sharing checkbox.
To select a specific folder to share, click the Add button  at the bottom of the Shared Folders list, locate the folder, select it, then click Add.
The Public folder of each user with an account on your Mac is shared automatically. To prevent a folder from being shared, select it in the Shared Folders list and click the Remove button .
Control-click the name of the folder, choose Advanced Options, select desired options, then click OK.
See Set advanced file sharing options.
By default, any user set up on your Mac in Users & Groups preferences can connect to your Mac over the network. A user with an administrator account can access your entire Mac.
To give only specific users or groups access to a folder, select the folder in the Shared Folders list, click the Add button  at the bottom of the Users list, then do one of the following:
Add users or groups from all users of your Mac: Select Users & Groups in the list on the left, select one or more names in the list on the right, then click Select.
Add users or groups from everyone on your network: Select Network Users or Network Groups in the list on the left, select one or more names in the list on the right, then click Select.
Add someone from your contacts and create a sharing-only account for them: Select Contacts in the list on the left, select a name in the list on the right, click Select, create a password, then click Create Account.
To specify the amount of access for a user, select the user in the Users list, click the pop-up menu next to the user name, then choose one of the following:
Read & Write: The user can see and copy files to and from the folder.
Read Only: The user can view the contents of the folder but can’t copy files to it.
Write Only (Drop Box): The user can copy files to the folder but can’t view its contents.
No Access: The user can’t see or copy files from the folder.