add stringlist function. They can be used to build a list

of strings. For now mainly useful to print the resulting
list in columns which is used in tab completion and ls.

include/stringlist.h

@@ -0,0 +1,27 @@
+#ifndef __STRING_H
+#define __STRING_H
+
+#include <list.h>
+
+struct string_list {
+	struct list_head list;
+	char str[0];
+};
+
+int string_list_add(struct string_list *sl, char *str);
+void string_list_print_by_column(struct string_list *sl);
+
+static inline void string_list_init(struct string_list *sl)
+{
+	INIT_LIST_HEAD(&sl->list);
+}
+
+static inline void string_list_free(struct string_list *sl)
+{
+	struct string_list *entry, *safe;
+
+	list_for_each_entry_safe(entry, safe, &sl->list, list)
+		free(entry);
+}
+
+#endif /* __STRING_H */

lib/Makefile

@@ -13,6 +13,7 @@ obj-y 			+= readkey.o
 obj-y			+= kfifo.o
 obj-y			+= libbb.o
 obj-y			+= libgen.o
+obj-y			+= stringlist.o
 obj-y			+= recursive_action.o
 obj-y			+= make_directory.o
 obj-$(CONFIG_BZLIB)	+= bzlib.o bzlib_crctable.o bzlib_decompress.o bzlib_huffman.o bzlib_randtable.o

lib/stringlist.c

@@ -0,0 +1,45 @@
+#include <common.h>
+#include <xfuncs.h>
+#include <malloc.h>
+#include <stringlist.h>
+
+int string_list_add(struct string_list *sl, char *str)
+{
+	struct string_list *new;
+
+	new = xmalloc(sizeof(struct string_list) + strlen(str) + 1);
+
+	strcpy(new->str, str);
+
+	list_add_tail(&new->list, &sl->list);
+
+	return 0;
+}
+
+void string_list_print_by_column(struct string_list *sl)
+{
+	int len = 0, num, i;
+	struct string_list *entry;
+
+	list_for_each_entry(entry, &sl->list, list) {
+		int l = strlen(entry->str) + 4;
+		if (l > len)
+			len = l;
+	}
+
+	if (!len)
+		return;
+
+	num = 80 / len;
+	if (len == 0)
+		len = 1;
+
+	i = 0;
+	list_for_each_entry(entry, &sl->list, list) {
+		printf("%-*s    ", len, entry->str);
+		if (!(++i % num))
+			printf("\n");
+	}
+	if (i % num)
+		printf("\n");
+}