harvey/sys/man/1/pipefile

.TH PIPEFILE 1
.SH NAME
pipefile \- attach filter to file in name space
.SH SYNOPSIS
.B pipefile
[
.B -d
] [
.B -r
.I command
] [
.B -w
.I command
]
.I file
.SH DESCRIPTION
.I Pipefile
uses
.IR bind (2)
to attach a pair of pipes to
.IR file ,
using them to
interpose filter
.I commands
between the true file and the simulated file that subsequently
appears in the name space.
Option
.B -r
interposes a filter that will affect the data delivered to programs that read from
.IR file ;
.B -w
interposes a filter that will affect the data written by programs to
.IR file .
At least one
.I command
must be specified;
.I pipefile
will insert a
.IR cat (1)
process in the other direction.
.PP
After
.I pipefile
has been run, the filters are established for programs that subsequently
open the
.IR file ;
programs already using the
.I file
are unaffected.
.PP
.I Pipefile
opens the
.I file
twice, once for each direction.  If the
.I file
is a single-use device, such as
.BR /dev/mouse ,
use the
.B -d
flag to specify that the file is to be opened once, in
.B ORDWR
mode.
.SH EXAMPLES
Simulate an old terminal:
.EX
.IP
% pipefile -w 'tr a-z A-Z' /dev/cons
% rc -i </dev/cons >/dev/cons >[2=1]
% echo hello
HELLO
%
.EE
.PP
Really simulate an old terminal:
.EX
.IP
% pipefile -r 'tr A-Z a-z' -w 'tr a-z A-Z' /dev/cons
% rc -i </dev/cons >/dev/cons >[2=1]
% DATE
THU OCT 12 10:13:45 EDT 2000
%
.EE
.SH SOURCE
.B /sys/src/cmd/pipefile.c
.SH SEE ALSO
.IR mouse (8)
.SH BUGS
The I/O model of
.I pipefile
is peculiar; it doesn't work well on plain files.
It is really intended for use with continuous devices such as
.I /dev/cons
and
.IR /dev/mouse .
.I Pipefile
should be rewritten to be a user-level file system.
.PP
If the program using the file managed by
.I pipefile
exits, the filter will see EOF and exit, and the file will be unusable
until the name space is repaired.