Portals in 4.4BSD

W. Richard Stevens
Consultant

Jan-Simon Pendry
Sequent UK

Abstract

Portals were added to 4.4BSD as an experi-
mental feature and are in the publicly available
4.4BSD-Lite distribution. Portals provide access to
alternate file types or devices using names in the nor-
mal filesystem that a process just opens. For exam-
ple, an open of /p/tcp/foo.com/smtp returns a
TCP socket descriptor to the calling process that is
connected to the SMTP server on the specified host.
By providing access through the normal filesystem,
the calling process need not be aware of the special
functions necessary to create a TCP socket and estab-
lish a TCP connection. This makes TCP connections,
for example, available to programs such as Awk, Tcl,
and shell scripts.
 
This paper describes the implementation of portals in
4.4BSD as another type of filesystem and provides some examples.
 

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