`$ brew install tree

`$ tree -d /proc/self/
/proc/self/
|-- attr
|-- cwd -\> /proc
|-- fd
| `-- 3 -> /proc/15589/fd
`|-- fdinfo
|-- net
| |-- dev_snmp6
| |-- netfilter
| |-- rpc
| | |-- auth.rpcsec.context
| | |-- auth.rpcsec.init
| | |-- auth.unix.gid
| | |-- auth.unix.ip
| | |-- nfs4.idtoname
| | |-- nfs4.nametoid
| | |-- nfsd.export
| | `-- nfsd.fh
`| `-- stat
`|-- root -\> /
`-- task
``-- 15589
`|-- attr
|-- cwd -\> /proc
|-- fd
| `-- 3 -> /proc/15589/task/15589/fd
`|-- fdinfo
`-- root -> /