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shred: implement -s SIZE

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function                                             old     new   delta
shred_main                                           337     391     +54
.rodata                                           103393  103395      +2
packed_usage                                       33666   33656     -10
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(add/remove: 0/0 grow/shrink: 2/1 up/down: 56/-10)             Total: 46 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2021-06-20 13:08:50 +02:00
parent 83dff7f431
commit ec3170ac95
1 changed files with 11 additions and 3 deletions
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14
coreutils/shred.c
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@ -15,14 +15,15 @@
//kbuild:lib-$(CONFIG_SHRED) += shred.o
//usage:#define shred_trivial_usage
//usage: "[-fuz] [-n N] FILE..."
//usage: "[-fuz] [-n N] [-s SIZE] FILE..."
//usage:#define shred_full_usage "\n\n"
//usage: "Overwrite/delete FILEs\n"
//usage: "\n -f Chmod to ensure writability"
//usage: "\n -s SIZE Size to write"
//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
//-x (exact: don't round up to 4k) and -v (verbose) are accepted but have no effect
/* shred (GNU coreutils) 8.25:
-f, --force change permissions to allow writing if necessary
@ -41,6 +42,7 @@
int shred_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int shred_main(int argc UNUSED_PARAM, char **argv)
{
char *opt_s;
int rand_fd = rand_fd; /* for compiler */
int zero_fd;
unsigned num_iter = 3;
@ -52,9 +54,10 @@ int shred_main(int argc UNUSED_PARAM, char **argv)
OPT_n = (1 << 3),
OPT_v = (1 << 4),
OPT_x = (1 << 5),
OPT_s = (1 << 6),
};
opt = getopt32(argv, "^" "fuzn:+vx" "\0" "-1"/*min 1 arg*/, &num_iter);
opt = getopt32(argv, "^" "fuzn:+vxs:" "\0" "-1"/*min 1 arg*/, &num_iter, &opt_s);
argv += optind;
zero_fd = xopen("/dev/zero", O_RDONLY);
@ -82,6 +85,11 @@ int shred_main(int argc UNUSED_PARAM, char **argv)
if (fstat(fd, &sb) == 0 && sb.st_size > 0) {
off_t size = sb.st_size;
if (opt & OPT_s) {
size = BB_STRTOOFF(opt_s, NULL, 0); /* accepts oct/hex */
if (errno || size < 0) bb_show_usage();
}
for (i = 0; i < num_iter; i++) {
bb_copyfd_size(rand_fd, fd, size);
fdatasync(fd);