.TH PIPEFS 4
.SH NAME
pipefs \- attach filters to a file system
.SH SYNOPSIS
.B pipefs
[
.B -a|-b
] [
.B -c
] [
.B -r
.I command
] [
.B -w
.I command
]
.I dir
.I mountpoint
.SH DESCRIPTION
.I Pipefs
acts as a filesystem layer above an existing name space,
attaching filters to the files in the name space.
.PP
.I Pipefs
makes the name space under
.I dir
visible at
.IR mountpoint .
The
.B -a
(or
.BR -b )
option causes the name
space to be placed after (or before) the current
contents of
.IR mountpoint ;
the default is to replace
the current contents.  The
.B -c
option permits
creation under
.IR mountpoint .
.PP
Data that is read from
(or written to) files made visible under
.I mountpoint
is filtered through
.IR command ,
specified using the
.B -r
(or
.BR -w )
option.  At least one
.I command
must be specified;
.I pipefs
will use
.IR cat (1)
as the
other
.IR command .
.SH EXAMPLE
To read / write encrypted files:
.IP
.EX
(pipefs -c -r 'crypt -d -k secret'
	-w 'crypt -k secret'
	/encrypted/dir /n/decrypted)
.EE
.SH SOURCE
.B /appl/cmd/pipefs.b
.SH "SEE ALSO"
.IR pipefile (1)
.SH BUGS
Not all error conditions are handled gracefully.
.br
The length of the original file, and not that of the filtered one, is returned in
.IR sys-stat (2).
