Add catv (separate applet instead of cat -v). Also cleanup cat.c comments,

the following of which (from cat.c) belongs in svn history instead of the
source code:

/* Mar 16, 2003      Manuel Novoa III   (mjn3@codepoet.org)
 *
 * This is a new implementation of 'cat' which aims to be SUSv3 compliant.
 *
 * Changes from the previous implementation include:
 * 1) Multiple '-' args are accepted as required by SUSv3.  The previous
 *    implementation would close stdin and segfault on a subsequent '-'.
 * 2) The '-u' options is required by SUSv3.  Note that the specified
 *    behavior for '-u' is done by default, so all we need do is accept
 *    the option.
 */

coreutils/catv.c

@@ -0,0 +1,65 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * cat -v implementation for busybox
+ *
+ * Copyright (C) 2006 Rob Landley <rob@landley.net>
+ *
+ * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
+ */
+
+/* See "Cat -v considered harmful" at
+ * http://cm.bell-labs.com/cm/cs/doc/84/kp.ps.gz */
+
+#include "busybox.h"
+#include <unistd.h>
+#include <fcntl.h>
+
+int catv_main(int argc, char **argv)
+{
+	int retval = EXIT_SUCCESS, fd, flags;
+
+	flags = bb_getopt_ulflags(argc, argv, "etv");
+	flags ^= 4;
+
+	// Loop through files.
+
+	argv += optind;
+	do {
+		// Read from stdin if there's nothing else to do.
+
+		fd = 0;
+		if (*argv && 0>(fd = bb_xopen(*argv, O_RDONLY))) retval = EXIT_FAILURE;
+		else for(;;) {
+			int i, res;
+
+			res = read(fd, bb_common_bufsiz1, sizeof(bb_common_bufsiz1));
+			if (res < 0) retval = EXIT_FAILURE;
+			if (res <1) break;
+			for (i=0; i<res; i++) {
+				char c=bb_common_bufsiz1[i];
+
+				if (c > 126 && (flags & 4)) {
+					if (c == 127) {
+						printf("^?");
+						continue;
+					} else {
+						printf("M-");
+						c -= 128;
+					}
+				}
+				if (c < 32) {
+					if (c == 10) {
+					   if (flags & 1) putchar('$');
+					} else if (flags & (c==9 ? 2 : 4)) {
+						printf("^%c", c+'@');
+						continue;
+					}
+				}
+				putchar(c);
+			}
+		}
+		if (ENABLE_FEATURE_CLEAN_UP && fd) close(fd);
+	} while (*++argv);
+
+	return retval;
+}