tac: *really* add tac.c now

coreutils/tac.c

@@ -0,0 +1,68 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * tac implementation for busybox
+ *
+ * Copyright (C) 2003  Yang Xiaopeng  <yxp at hanwang.com.cn>
+ * Copyright (C) 2007  Natanael Copa  <natanael.copa@gmail.com>
+ * Copyright (C) 2007  Tito Ragusa    <farmatito@tiscali.it>
+ *
+ * Licensed under GPLv2, see file License in this tarball for details.
+ *
+ */
+
+/* tac - concatenate and print files in reverse */
+
+/* Based on Yang Xiaopeng's (yxp at hanwang.com.cn) patch
+ * http://www.uclibc.org/lists/busybox/2003-July/008813.html
+ */
+
+#include "libbb.h"
+
+/* This is a NOEXEC applet. Be very careful! */
+
+int tac_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int tac_main(int argc, char **argv)
+{
+	char **name;
+	FILE *f;
+	char *line;
+	llist_t *list = NULL;
+	int retval = EXIT_SUCCESS;
+	
+	argv++;
+	if (!*argv)
+		*--argv = (char *)"-";
+	/* We will read from last file to first */
+	name = argv;
+	while (*name)
+		name++;
+
+	do {
+		name--;
+		f = fopen_or_warn_stdin(*name);
+		if (f == NULL) {
+			retval = EXIT_FAILURE;
+			continue;
+		}
+
+		errno = 0;
+		/* FIXME: NUL bytes are mishandled. */
+		while ((line = xmalloc_fgets(f)) != NULL)
+			llist_add_to(&list, line);	
+
+		/* xmalloc_fgets uses getc and returns NULL on error or EOF. */
+		/* It sets errno to ENOENT on EOF, but fopen_or_warn_stdin would */
+		/* catch this error so we can filter it out here. */
+		if (errno && errno != ENOENT) {
+			bb_simple_perror_msg(*name);
+			retval = EXIT_FAILURE;
+		}
+	} while (name != argv);
+
+	while (list) {
+		printf("%s", list->data);
+		list = list->link;
+	}
+	
+	return retval;
+}