18 Nov
2017
18 Nov
'17
4:09 p.m.
Hi Norman,
...
ed(1)
pre-dates pipes. When pipes came along, stderr was needed,
and lots of new idioms were found to make use of them. Why didn't
ed gain a `filter' command to accompany `r !foo' and `w !bar'?
I sometimes wonder that too.
When I use `ed,' it is usually really qed, an extended ed written by
the late-1970s UNIX crowd here at U of T. -- The ability to send part or all of a buffer to a
shell command, to
read data in from a shell command, or to send data out and replace it
with that from the shell command:
Thanks for the pointer.
I dug a little. 7th Ed. ed doesn't have the `:[rw] !foo' form. It was
in "PDP-11 3+2", 1983-01, in filename().
http://minnie.tuhs.org/cgi-bin/utree.pl?file=pdp11v/usr/src/cmd/ed/ed.c
Xqt is the global flag that says the `!' was present.
By the time of ex, that did have a filter, the `:w !foo' applied the
`:se nu list' settings to the output of the command, and ex also appends
a LF if the command's output doesn't end with one. The effect, if not
the implementation, is as if the command's output was in a temporary
buffer than was `%p'-ed. Here's ex-reimplementation nvi 1.79's attempt
at POSIX's
http://pubs.opengroup.org/onlinepubs/9699919799/utilities/ex.html#tag_20_40…
:se nu list
:a
1 foo bar
2 xyzzy
3 .
:w !head -c 10
foo^Ibar
xy
!
So the line numbers are missing, but it's partly done the `se list' by
showing the tab, though `$' to mark the EOF is missing, and it has added
the LF.
--
Cheers, Ralph.
https://plus.google.com/+RalphCorderoy
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