diff -uNr renameutils-0.12.0/src/editformats/getsubopt.c renameutils-0.12.0.mod/src/editformats/getsubopt.c
--- renameutils-0.12.0/src/editformats/getsubopt.c	1970-01-01 03:00:00.000000000 +0300
+++ renameutils-0.12.0.mod/src/editformats/getsubopt.c	2020-01-02 20:56:21.548067937 +0200
@@ -0,0 +1,59 @@
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+char *suboptarg;
+
+int
+getsubopt(optionp, tokens, valuep)
+	char **optionp, **valuep;
+	char * const *tokens;
+{
+	int cnt;
+	char *p;
+
+	/* optionp is tested below */
+
+	suboptarg = *valuep = NULL;
+
+	if (!optionp || !*optionp)
+		return(-1);
+
+	/* skip leading white-space, commas */
+	for (p = *optionp; *p && (*p == ',' || *p == ' ' || *p == '\t'); ++p);
+
+	if (!*p) {
+		*optionp = p;
+		return(-1);
+	}
+
+	/* save the start of the token, and skip the rest of the token. */
+	for (suboptarg = p;
+	    *++p && *p != ',' && *p != '=' && *p != ' ' && *p != '\t';);
+
+	if (*p) {
+		/*
+		 * If there's an equals sign, set the value pointer, and
+		 * skip over the value part of the token.  Terminate the
+		 * token.
+		 */
+		if (*p == '=') {
+			*p = '\0';
+			for (*valuep = ++p;
+			    *p && *p != ',' && *p != ' ' && *p != '\t'; ++p);
+			if (*p) 
+				*p++ = '\0';
+		} else
+			*p++ = '\0';
+		/* Skip any whitespace or commas after this token. */
+		for (; *p && (*p == ',' || *p == ' ' || *p == '\t'); ++p);
+	}
+
+	/* set optionp for next round. */
+	*optionp = p;
+
+	for (cnt = 0; *tokens; ++tokens, ++cnt)
+		if (!strcmp(suboptarg, *tokens))
+			return(cnt);
+	return(-1);
+}
diff -uNr renameutils-0.12.0/src/editformats/Makefile.am renameutils-0.12.0.mod/src/editformats/Makefile.am
--- renameutils-0.12.0/src/editformats/Makefile.am	2012-04-23 14:11:26.000000000 +0300
+++ renameutils-0.12.0.mod/src/editformats/Makefile.am	2020-01-02 20:54:12.826838061 +0200
@@ -9,4 +9,5 @@
 lib_editformats_a_SOURCES = \
   destination-only.c \
   dual-column.c \
-  single-column.c
+  single-column.c \
+  getsubopt.c
diff -uNr renameutils-0.12.0/src/editformats/Makefile.in renameutils-0.12.0.mod/src/editformats/Makefile.in
--- renameutils-0.12.0/src/editformats/Makefile.in	2012-04-23 14:24:11.000000000 +0300
+++ renameutils-0.12.0.mod/src/editformats/Makefile.in	2020-01-02 20:55:04.196335228 +0200
@@ -154,7 +154,7 @@
 lib_editformats_a_AR = $(AR) $(ARFLAGS)
 lib_editformats_a_LIBADD =
 am_lib_editformats_a_OBJECTS = destination-only.$(OBJEXT) \
-	dual-column.$(OBJEXT) single-column.$(OBJEXT)
+	dual-column.$(OBJEXT) single-column.$(OBJEXT) getsubopt.$(OBJEXT)
 lib_editformats_a_OBJECTS = $(am_lib_editformats_a_OBJECTS)
 DEFAULT_INCLUDES = -I.@am__isrc@ -I$(top_builddir)
 depcomp = $(SHELL) $(top_srcdir)/build-aux/depcomp
@@ -979,7 +979,8 @@
 lib_editformats_a_SOURCES = \
   destination-only.c \
   dual-column.c \
-  single-column.c
+  single-column.c \
+  getsubopt.c
 
 all: all-am
 
