Add barebones lsusb(8)

Makefile

@@ -25,6 +25,7 @@ SRC = \
 	halt.c              \
 	insmod.c            \
 	lsmod.c             \
+	lsusb.c             \
 	mkswap.c            \
 	mount.c             \
 	mountpoint.c        \

lsusb.c

@@ -0,0 +1,55 @@
+/* See LICENSE file for copyright and license details. */
+#include <stdio.h>
+#include <stdlib.h>
+#include <limits.h>
+#include "util.h"
+
+static void lsusb(const char *file);
+
+static void
+usage(void)
+{
+	eprintf("usage: %s\n", argv0);
+}
+
+int
+main(int argc, char *argv[])
+{
+	ARGBEGIN {
+	default:
+		usage();
+	} ARGEND;
+
+	recurse("/sys/bus/usb/devices", lsusb);
+	return 0;
+}
+
+static void
+lsusb(const char *file)
+{
+	FILE *fp;
+	char *cwd;
+	char path[PATH_MAX];
+	char buf[BUFSIZ];
+	int busnum, devnum, pid, vid;
+	int i = 0;
+
+	cwd = agetcwd();
+	snprintf(path, sizeof(path), "%s/%s/uevent", cwd, file);
+	free(cwd);
+	if (!(fp = fopen(path, "r")))
+		return;
+	while (fgets(buf, sizeof(buf), fp)) {
+		if (sscanf(buf, "BUSNUM=%u\n", &busnum) ||
+		    sscanf(buf, "DEVNUM=%u\n", &devnum) ||
+		    sscanf(buf, "PRODUCT=%x/%x/", &pid, &vid))
+			i++;
+		if (i == 3) {
+			printf("Bus %03d Device %03d: ID %04x:%04x\n", busnum, devnum,
+			       pid, vid);
+			break;
+		}
+	}
+	fclose(fp);
+}
+