Merge patch series "regex patches"

Rasmus Villemoes <ravi@prevas.dk> says:

This started as a rather simple patch, 1/12, adding the ability to
more conveniently do regex matching in shell.

But with that, it became very easy to see what the slre library can
and especially what it cannot do, and that way I found both outright
bugs and a "wow, doesn't it support that syntax" gotcha. I couldn't
find any tests ('git grep slre -- test/' was empty), so I added a
small test suite and tweaked slre.c.

Link: https://lore.kernel.org/r/20250513084034.654865-1-ravi@prevas.dk

cmd/test.c

@@ -7,6 +7,7 @@
 #include <command.h>
 #include <fs.h>
 #include <log.h>
+#include <slre.h>
 #include <vsprintf.h>
 
 #define OP_INVALID	0
@@ -26,6 +27,7 @@
 #define OP_INT_GT	14
 #define OP_INT_GE	15
 #define OP_FILE_EXISTS	16
+#define OP_REGEX	17
 
 const struct {
 	int arg;
@@ -49,6 +51,9 @@ const struct {
 	{0, "-z", OP_STR_EMPTY, 2},
 	{0, "-n", OP_STR_NEMPTY, 2},
 	{0, "-e", OP_FILE_EXISTS, 4},
+#ifdef CONFIG_REGEX
+	{1, "=~", OP_REGEX, 3},
+#endif
 };
 
 static int do_test(struct cmd_tbl *cmdtp, int flag, int argc,
@@ -141,6 +146,20 @@ static int do_test(struct cmd_tbl *cmdtp, int flag, int argc,
 		case OP_FILE_EXISTS:
 			expr = file_exists(ap[1], ap[2], ap[3], FS_TYPE_ANY);
 			break;
+#ifdef CONFIG_REGEX
+		case OP_REGEX: {
+			struct slre slre;
+
+			if (slre_compile(&slre, ap[2]) == 0) {
+				printf("Error compiling regex: %s\n", slre.err_str);
+				expr = 0;
+				break;
+			}
+
+			expr = slre_match(&slre, ap[0], strlen(ap[0]), NULL);
+			break;
+		}
+#endif
 		}
 
 		switch (op) {