mdev: optional support for regex pattern group substitution.

+142 bytes.

2 files changed, 48 insertions, 3 deletions

diff --git a/util-linux/Config.in b/util-linux/Config.in
index 1f4322bec..869ec61d5 100644
--- a/util-linux/Config.in
+++ b/util-linux/Config.in
@@ -321,6 +321,13 @@ config FEATURE_MDEV_RENAME
 
 	  For more information, please see docs/mdev.txt
 
+config FEATURE_MDEV_RENAME_REGEXP
+	bool "Support regular expressions substitutions when renaming device"
+	default n
+	depends on FEATURE_MDEV_RENAME
+	help
+	  Add support for regular expressions substitutions when renaming device.
+
 config FEATURE_MDEV_EXEC
 	bool "Support command execution at device addition/removal"
 	default n
diff --git a/util-linux/mdev.c b/util-linux/mdev.c
index c8d603bcf..9d77f6a1f 100644
--- a/util-linux/mdev.c
+++ b/util-linux/mdev.c
@@ -84,6 +84,8 @@ static void make_device(char *path, int delete)
 			goto end_parse;
 
 		while ((line = xmalloc_fgetline(fp)) != NULL) {
+			regmatch_t off[1+9*ENABLE_FEATURE_MDEV_RENAME_REGEXP];
+
 			++lineno;
 			trim(line);
 			if (!line[0])
@@ -95,16 +97,24 @@ static void make_device(char *path, int delete)
 			next = next_field(line);
 			{
 				regex_t match;
-				regmatch_t off;
 				int result;
 
 				/* Is this it? */
 				xregcomp(&match, line, REG_EXTENDED);
-				result = regexec(&match, device_name, 1, &off, 0);
+				result = regexec(&match, device_name, ARRAY_SIZE(off), off, 0);
 				regfree(&match);
 
+				//bb_error_msg("matches:");
+				//for (int i = 0; i < ARRAY_SIZE(off); i++) {
+				//	if (off[i].rm_so < 0) continue;
+				//	bb_error_msg("match %d: '%.*s'\n", i,
+				//		(int)(off[i].rm_eo - off[i].rm_so),
+				//		device_name + off[i].rm_so);
+				//}
+
 				/* If not this device, skip rest of line */
-				if (result || off.rm_so || off.rm_eo != strlen(device_name))
+				/* (regexec returns whole pattern as "range" 0) */
+				if (result || off[0].rm_so || off[0].rm_eo != strlen(device_name))
 					goto next_line;
 			}
 
@@ -152,7 +162,35 @@ static void make_device(char *path, int delete)
 				val = next;
 				next = next_field(val);
 				if (*val == '>') {
+#if ENABLE_FEATURE_MDEV_RENAME_REGEXP
+					/* substitute %1..9 with off[1..9], if any */
+					char *s, *p;
+					unsigned i, n;
+
+					n = 0;
+					s = val;
+					while (*s && *s++ == '%')
+						n++;
+					
+					p = alias = xzalloc(strlen(val) + n * strlen(device_name));
+					s = val + 1;
+					while (*s) {
+						*p = *s;
+						if ('%' == *s) {
+							i = (s[1] - '0');
+							if (i <= 9 && off[i].rm_so >= 0) {
+								n = off[i].rm_eo - off[i].rm_so;
+								strncpy(p, device_name + off[i].rm_so, n);
+								p += n - 1;
+								s++;
+							}
+						}
+						p++;
+						s++;
+					}
+#else
 					alias = xstrdup(val + 1);
+#endif
 				}
 			}