>From `man ed`
If replacement consists of a single `%', then
replacement from the last substitution is used
However, there seems to be a bug in this if the closing delimiter isn't
provided.
Normally the closing replacement delimiter is optional:
s/foo/bar/
s/foo/bar
(both replace "foo" with "bar") However using "%" per the man-page seems
to require the closing delimiter. To demonstrate
$ cat test.txt
a
b
c
$ ed test.txt
6
1s/a/hello
hello
2/s/b/%
%
,n
1 hello
2 %
3 c
Q
$ ed test.txt
6
1s/a/hello
hello
2/s/b/%/
,n
1 hello
2 hello
3 c
Q
So the biggest issue is that, without the trailing slash, it replaces
with "%" rather than the last replacement text. As a minor side-note,
when using the most recent replacement (with the slash), it doesn't
print the resulting line the same way it does with a normal substitution
(i.e., note that the first example prints the "%", while the second
emits nothing)
It looks like src/bin/ed/sub.c:89 has the test
if (*ibufp == '%' && *(ibufp + 1) == delimiter) {
which should likely be something like (untested)
if (*ibufp == '%' && (*(ibufp + 1) == delimiter || *(ibufp + 1) == '\0')) {
FWIW, this bug appears in FreeBSD's ed(1) as well
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=284434
Thanks!
-tkc
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