🚀 go-pugleaf

In article <165@xyzzy.UUCP> throopw@xyzzy.UUCP (Wayne A. Throop) writes:
>
>> peter@sugar.UUCP (Peter da Silva)
>> [...] you can describe some pipelines graphically that you would have a great
>> deal of trouble expressing on a command line.
>>
>> (awk)_______                                 _(one set of lines)
>>             \__(sort both together)|(grep2)_/
>> (sort|grep)_/                               \_(another set of lines)
>> 
>> Every now and then I come across something wierd like this I want to do.
>> I usually end up making temp files. Wasn't that the whole point of pipes
>> in the first place?
>
> [Wayne gives an involved solution using tee and multiple file descriptors.]

There exists a notation to do this in ksh-i, the latest version of ksh. To
use it though, your Unix must have the V8 /dev/fd  mechanism (keep an eye
on comp.sources.unix for a driver for 4.3 & NFS systems, from me, originally
from Fred Blonder). Anyway the notation is

	sort (awk) (sort | grep)

The ()'s enclose a shell pipeline, if preceded by a '<' or left alone,
the pipline's output is connected to a file in /dev/fd passed as the argument
to the program. The file will be the read end of a pipe, so sort would
see, e.g., "/dev/fd/4" and "/dev/fd/5" for its arguments, awk and the 
sort|grep pipeline would write on the other side of the pipe.

Such a pipeline may be written to as well:

	command | tee >(prog1) >(prog2)

would send command's output to both prog1 and prog2.

There is no existing Unix tool that corresponds to the 'grep2' in Peter's
example above.
-- 
Arnold Robbins
ARPA, CSNET:	arnold@emory.ARPA	BITNET: arnold@emory
UUCP:	{ decvax, gatech, sun!sunatl }!emory!arnold
ONE-OF-THESE-DAYS:	arnold@emory.mathcs.emory.edu