busybox

/* 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);

​