[TAG] 2c tip: filtering in-place
Jay R. Ashworth
jra at baylink.com
Fri Mar 19 21:44:22 MSK 2004
On Fri, Mar 19, 2004 at 10:39:34AM -0500, Ben Okopnik wrote:
> On Fri, Mar 19, 2004 at 02:33:21PM +0530, Kapil Hari Paranjape wrote:
> > I have always thought that filtering files "in-place" was
> > not possible from the command line...
> > ...until today---one lives and learns.
> > dd if=file bs=4k | filter | dd of=file bs=4k conv=notrunc
> > Where "file" is the file you want to filter and "filter"
> > is the filtering program you want to apply.
> The "buffer" program does exactly the same as the above; the process is
> called "reblocking".
> buffer < foo | filter > foo
<interrupts self while raising hand to complain>
Oh, cause buffer reads the entire file before the '>' can stomp it?
Well, that's not *exactly* the same... :-)
Doesn't that still depend on order of evaluation by the shell? Is that
Jay R. Ashworth jra at baylink.com
Member of the Technical Staff Baylink RFC 2100
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