[PATCH 2/2 v6] truncate: new applet

[Ari Sundholm]

From: Ari Sundholm <ari at tuxera.com>

bloat-o-meter:

function                                             old     new   delta
truncate_main                                          -     160    +160
.rodata                                           154411  154458     +47
packed_usage                                       30197   30214     +17
applet_names                                        2483    2492      +9
applet_main                                         2888    2896      +8
applet_nameofs                                       722     724      +2
------------------------------------------------------------------------------
(add/remove: 2/0 grow/shrink: 5/0 up/down: 243/0)             Total: 243 bytes

v2: Make dd and truncate share a common suffix struct.
v3: Split suffix struct move into separate commit, make applet NOFORK, adjust
    error message.
v4: Use bb_error_msg_and_die() instead of bb_error_msg() + xfunc_die().
v5: Add correct bloat-o-meter data.
v6: Use opt_complementary to check the presence of filenames, juggle the flags
    to xopen() and shorten an error message.

Signed-off-by: Ari Sundholm <ari at tuxera.com>
---
 coreutils/truncate.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100644 coreutils/truncate.c

diff --git a/coreutils/truncate.c b/coreutils/truncate.c
new file mode 100644
index 0000000..1f2bc01
--- /dev/null
+++ b/coreutils/truncate.c
@@ -0,0 +1,70 @@
+/*
+ * Mini truncate implementation for busybox
+ *
+ * Copyright (C) 2015 by Ari Sundholm <ari at 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-$(CONFIG_TRUNCATE) += truncate.o
+//applet:IF_TRUNCATE(APPLET_NOFORK(truncate, truncate, BB_DIR_USR_BIN, BB_SUID_DROP, truncate))
+
+//usage:#define truncate_trivial_usage
+//usage:       "[-c] -s SIZE FILE..."
+//usage:#define truncate_full_usage "\n\n"
+//usage:	"Truncate FILEs to the given size.\n"
+//usage:	"\n	-c	Do not create any files."
+//usage:	"\n	-s SIZE	Truncate to SIZE."
+//usage:
+//usage:#define truncate_example_usage
+//usage:	"$ 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 fd;
+	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;
+
+	size = XATOU_SFX(size_str, cwbkMG_suffixes);
+
+	argv += optind;
+	while (*argv) {
+		fd = xopen(*argv, flags);
+		if (ftruncate(fd, size) == -1)
+			bb_perror_msg_and_die("ftruncate");
+		xclose(fd);
+		++argv;
+	}
+
+	return 0;
+}
-- 
1.9.1