shithub: purgatorio

ref: 94443daf8e248e65afc8d3f17f26efea22748b51
dir: purgatorio/man/4/ramfile

.TH RAMFILE 4
.SH NAME
ramfile \- synthesise file
.SH SYNOPSIS
.B ramfile
.I file
[
.I data
]
.SH DESCRIPTION
.I Ramfile
puts a virtual file in the name space at
.IR file ,
and services file requests on it.
Data written to the file is stored in
.IR ramfile 's
memory; read requests return the previously stored data.
If the optional
.I data
argument is provided, the file will initially contain that text.
The parent directory of
.I file
must exist;
.I ramfile
creates a union mount on that directory, and if
.I file
previously existed, the synthesised file will hide it.
.PP
.I Ramfile
uses
.IR sys-file2chan (2),
which simplifies implementation but prevents it from knowing
when the file has been truncated.
Instead, it truncates the file on any write to the start of the file
(offset 0),
allowing
.IR cp (1)
to copy in new contents, and
text editors to edit it.
Indeed, the file will be usable by all applications that do
not rely on updating parts of the file in place, or if they do,
do not update the start of the file.
.SH SOURCE
.B /appl/cmd/ramfile.b
.SH SEE ALSO
.IR bind (1),
.IR sys-file2chan (2),
.IR srv (3),
.IR memfs (4)
.SH BUGS
.I Ramfile
cannot tell when the
.I path
has been unmounted;
the only option is to
.IR kill (1)
it.
.br
The
.I file
always appears to have zero length to
.IR sys-stat (2),
which prevents loading a Dis file from it.