NAME

pipefile − attach filter to file in name space

SYNOPSIS

­pipefile [ ­-d ] [ ­-r ­command ] [ ­-w ­command ] ­file

DESCRIPTION

­Pipefile uses bind(2) to attach a pair of pipes to file, using them to interpose filter ­commands between the true file and the simulated file that subsequently appears in the name space.  Option ­-r interposes a filter that will affect the data delivered to programs that read from file; ­-w interposes a filter that will affect the data written by programs to file. At least one ­command must be specified; ­pipefile will insert a cat(1) process in the other direction.

After ­pipefile has been run, the filters are established for programs that subsequently open the file; programs already using the ­file are unaffected. 

­Pipefile opens the ­file twice, once for each direction.  If the ­file is a single-use device, such as /dev/mouse, use the ­-d flag to specify that the file is to be opened once, in ­ORDWR mode. 

EXAMPLES

Simulate an old terminal:

% pipefile -w ’tr a-z A-Z’ /dev/cons
% rc -i </dev/cons >/dev/cons >[2=1]
% echo hello
HELLO
%

Really simulate an old terminal:

% 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
%

SOURCE

­/sys/src/cmd/pipefile.c

SEE ALSO

mouse(8)

BUGS

The I/O model of ­pipefile is peculiar; it doesn’t work well on plain files.  It is really intended for use with continuous devices such as ­/dev/cons and /dev/mouse. ­Pipefile should be rewritten to be a user-level file system. 

If the program using the file managed by ­pipefile exits, the filter will see EOF and exit, and the file will be unusable until the name space is repaired. 

Plan 9  —  March 15, 2001