shred: new applet

function                                             old     new   delta
shred_main                                             -     361    +361
packed_usage                                       31427   31467     +40
applet_names                                        2578    2584      +6
applet_main                                         1492    1496      +4
run_applet_and_exit                                  679     682      +3
------------------------------------------------------------------------------
(add/remove: 2/0 grow/shrink: 4/0 up/down: 414/0)             Total: 414 bytes

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

2 files changed, 106 insertions, 2 deletions

diff --git a/coreutils/cksum.c b/coreutils/cksum.c
index aeec0188d..9034fc19a 100644
--- a/coreutils/cksum.c
+++ b/coreutils/cksum.c
@@ -17,9 +17,9 @@
 //kbuild:lib-$(CONFIG_CKSUM) += cksum.o
 
 //usage:#define cksum_trivial_usage
-//usage:       "FILES..."
+//usage:       "FILE..."
 //usage:#define cksum_full_usage "\n\n"
-//usage:       "Calculate the CRC32 checksums of FILES"
+//usage:       "Calculate the CRC32 checksums of FILEs"
 
 #include "libbb.h"
 #include "common_bufsiz.h"
diff --git a/coreutils/shred.c b/coreutils/shred.c
new file mode 100644
index 000000000..9cd39b79c
--- /dev/null
+++ b/coreutils/shred.c
@@ -0,0 +1,104 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Copyright (C) 2017 Denys Vlasenko <vda.linux@googlemail.com>
+ *
+ * Licensed under GPLv2, see file LICENSE in this source tree.
+ */
+//config:config SHRED
+//config:       bool "shred"
+//config:       default y
+//config:       help
+//config:         Overwrite a file to hide its contents, and optionally delete it
+
+//applet:IF_SHRED(APPLET(shred, BB_DIR_USR_BIN, BB_SUID_DROP))
+
+//kbuild:lib-$(CONFIG_SHRED) += shred.o
+
+//usage:#define shred_trivial_usage
+//usage:       "FILE..."
+//usage:#define shred_full_usage "\n\n"
+//usage:       "Overwrite/delete FILEs\n"
+//usage:     "\n        -f      Chmod to ensure writability"
+//usage:     "\n        -n N    Overwrite N times (default 3)"
+//usage:     "\n        -z      Final overwrite with zeros"
+//usage:     "\n        -u      Remove file"
+//-x and -v are accepted but have no effect
+
+/* shred (GNU coreutils) 8.25:
+-f, --force             change permissions to allow writing if necessary
+-u                      truncate and remove file after overwriting
+-z, --zero              add a final overwrite with zeros to hide shredding
+-n, --iterations=N      overwrite N times instead of the default (3)
+-v, --verbose           show progress
+-x, --exact             do not round file sizes up to the next full block; this is the default for non-regular files
+--random-source=FILE    get random bytes from FILE
+-s, --size=N            shred this many bytes (suffixes like K, M, G accepted)
+--remove[=HOW]          like -u but give control on HOW to delete;  See below
+*/
+
+#include "libbb.h"
+
+int shred_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int shred_main(int argc UNUSED_PARAM, char **argv)
+{
+        int rand_fd = rand_fd; /* for compiler */
+        int zero_fd;
+        unsigned num_iter = 3;
+        unsigned opt;
+        enum {
+                OPT_f = (1 << 0),
+                OPT_u = (1 << 1),
+                OPT_z = (1 << 2),
+                OPT_n = (1 << 3),
+                OPT_v = (1 << 4),
+                OPT_x = (1 << 5),
+        };
+
+        opt = getopt32(argv, "fuzn:+vx", &num_iter);
+        argv += optind;
+
+        zero_fd = xopen("/dev/zero", O_RDONLY);
+        if (num_iter != 0)
+                rand_fd = xopen("/dev/urandom", O_RDONLY);
+
+        if (!*argv)
+                bb_show_usage();
+
+        for (;;) {
+                struct stat sb;
+                unsigned i;
+                int fd = -1;
+
+                if (opt & OPT_f) {
+                        fd = open(*argv, O_WRONLY);
+                        if (fd < 0)
+                                chmod(*argv, 0666);
+                }
+                if (fd < 0)
+                        fd = xopen(*argv, O_WRONLY);
+
+                if (fstat(fd, &sb) == 0 && sb.st_size > 0) {
+                        off_t size = sb.st_size;
+
+                        for (i = 0; i < num_iter; i++) {
+                                bb_copyfd_size(rand_fd, fd, size);
+                                fdatasync(fd);
+                                xlseek(fd, 0, SEEK_SET);
+                        }
+                        if (opt & OPT_z) {
+                                bb_copyfd_size(zero_fd, fd, size);
+                                fdatasync(fd);
+                        }
+                        if (opt & OPT_u) {
+                                ftruncate(fd, 0);
+                                xunlink(*argv);
+                        }
+                        xclose(fd);
+                }
+                argv++;
+                if (!*argv)
+                        break;
+        }
+
+        return EXIT_SUCCESS;
+}