truncate: new applet

Add the actual new source file :(

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

coreutils/truncate.c

@@ -0,0 +1,77 @@
+/*
+ * Mini truncate implementation for busybox
+ *
+ * Copyright (C) 2015 by Ari Sundholm <ari@tuxera.com>
+ *
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
+ */
+
+//config:config TRUNCATE
+//config:	bool "truncate"
+//config:	default y
+//config:	help
+//config:	  truncate truncates files to a given size. If a file does
+//config:	  not exist, it is created unless told otherwise.
+
+//kbuild:lib-$(CONFIG_TRUNCATE) += truncate.o
+//applet:IF_TRUNCATE(APPLET_NOFORK(truncate, truncate, BB_DIR_USR_BIN, BB_SUID_DROP, truncate))
+
+//usage:#define truncate_trivial_usage
+//usage:       "[-c] -s SIZE FILE..."
+//usage:#define truncate_full_usage "\n\n"
+//usage:	"Truncate FILEs to the given size\n"
+//usage:	"\n	-c	Do not create files"
+//usage:	"\n	-s SIZE	Truncate to SIZE"
+//usage:
+//usage:#define truncate_example_usage
+//usage:	"$ truncate -s 1G foo"
+
+#include "libbb.h"
+
+#if ENABLE_LFS
+# define XATOU_SFX xatoull_sfx
+#else
+# define XATOU_SFX xatoul_sfx
+#endif
+
+/* This is a NOFORK applet. Be very careful! */
+
+int truncate_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int truncate_main(int argc UNUSED_PARAM, char **argv)
+{
+	unsigned opts;
+	int flags = O_RDWR;
+	int ret = EXIT_SUCCESS;
+	char *size_str;
+	off_t size;
+
+	enum {
+		OPT_NOCREATE  = (1 << 0),
+		OPT_SIZE = (1 << 1),
+	};
+
+	opt_complementary = "s:-1";
+	opts = getopt32(argv, "cs:", &size_str);
+
+	if (!(opts & OPT_NOCREATE))
+		flags |= O_CREAT;
+
+	// TODO: coreutils 8.17 also support "m" (lowercase) suffix
+	// with truncate, but not with dd!
+	// We share kMG_suffixes[], so we can't make both tools
+	// compatible at once...
+	size = XATOU_SFX(size_str, kMG_suffixes);
+
+	argv += optind;
+	while (*argv) {
+		int fd = xopen(*argv, flags);
+		if (ftruncate(fd, size) == -1) {
+			bb_perror_msg("%s: ftruncate", *argv);
+			ret = EXIT_FAILURE;
+		}
+		xclose(fd);
+		++argv;
+	}
+
+	return ret;
+}