Implement the @R parameter transformation to reverse the order of
list-valued parameter expansions.
This applies to array and positional parameter expansions such as
${param[@]@R}, ${param[*]@R}, ${@@R}, and ${*@R}.
The transformation preserves existing quoting, joining, and word-splitting
semantics for each expansion form. Scalar parameter expansions are
unchanged.
---
subst.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/subst.c b/subst.c
index dd5d57b..2532713 100644
--- a/subst.c
+++ b/subst.c
@@ -8771,6 +8771,9 @@ string_transform (int xc, SHELL_VAR *v, char *s)
case 'Q':
ret = sh_quote_reusable (s, 0);
break;
+ case 'R':
+ ret = savestring (s);
+ break;
case 'U':
ret = sh_modcase (s, 0, CASE_UPPER);
break;
@@ -8802,7 +8805,11 @@ list_transform (int xc, SHELL_VAR *v, WORD_LIST *list,
int itype, int quoted)
w->word = tword ? tword : savestring (""); /* XXX */
new = make_word_list (w, new);
}
- l = REVERSE_LIST (new, WORD_LIST *);
+
+ /* ${name[@]@R} and ${name[*]@R}: keep the list in the reverse
+ order produced by prepending above. Other transformations preserve
+ the original order by reversing NEW back. */
+ l = (xc == 'R') ? new : REVERSE_LIST (new, WORD_LIST *);
qflags = quoted;
/* If we are expanding in a context where word splitting will not be
@@ -8910,6 +8917,7 @@ valid_parameter_transform (const char *xform)
case 'E': /* expand like $'...' */
case 'P': /* expand like prompt string */
case 'Q': /* quote reusably */
+ case 'R': /* reverse array or positional parameter order */
case 'U': /* transform to uppercase */
case 'u': /* transform by capitalizing */
case 'L': /* transform to lowercase */
--
2.53.0
