From 4cf3658034ae37d432361f1084c88834e74e640b Mon Sep 17 00:00:00 2001
From: Your Name <you@example.com>
Date: Sun, 15 Oct 2023 11:29:56 +0300
Subject: [PATCH] yes

---
 TODO              |   2 -
 coreutils/shred.c | 109 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 109 insertions(+), 2 deletions(-)
 create mode 100644 coreutils/shred.c

diff --git a/TODO b/TODO
index 9f4003e..1329940 100644
--- a/TODO
+++ b/TODO
@@ -4,8 +4,6 @@ printf
 shuf
 id
 ln
-cp
-shred
 du
 df
 dd
diff --git a/coreutils/shred.c b/coreutils/shred.c
new file mode 100644
index 0000000..9794257
--- /dev/null
+++ b/coreutils/shred.c
@@ -0,0 +1,109 @@
+#include <stdio.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+
+#define RAND_SOURCE "/dev/urandom"
+#define ZERO_SOURCE "/dev/zero"
+
+unsigned int f_flag;
+unsigned int u_flag;
+unsigned int z_flag;
+unsigned int n_loops;
+
+int shred(int rand_fd, int zero_fd, int fd, unsigned int iter) {
+	off_t size = lseek(fd, 0, SEEK_END);
+	if (size < 0)
+		return 1;
+
+	lseek(fd, 0, SEEK_SET);
+
+	char buf[1];
+	while (size) {
+		if (iter == n_loops && z_flag)
+			read(zero_fd, buf, sizeof(buf));
+
+		else
+			read(rand_fd, buf, sizeof(buf));
+
+		write(fd, buf, sizeof(buf));
+		size--;
+	}
+
+	fsync(fd);
+	return 0;
+}
+
+int main(const int argc, const char **argv) {
+	n_loops = 3;
+	int i;
+
+	for (i = 1; i < argc; i++) {
+		if (argv[i][0] != '-')
+			break;
+
+		else if (!strcmp(argv[i], "-f"))
+			f_flag = 1;
+
+		else if (!strcmp(argv[i], "-u"))
+			u_flag = 1;
+
+		else if (!strcmp(argv[i], "-z"))
+			z_flag = 1;
+
+		else if (!strncmp(argv[i], "-n=", 3)) {
+			char *val = strchr(argv[i], '=');
+			if (!val)
+				break;
+
+			val[0] = '\0';
+			n_loops = atoi(val + 1);
+		}
+
+		else if (!strcmp(argv[i], "-h")) {
+			printf("shred [-n=N (Overwrite N times (default 3))] [-z (Final overwrite with zeros)] [-u (Remove file)] [-f (Chmod to ensure writability)] [FILE...]\n");
+			return 1;
+		}
+	}
+
+
+	int rand_fd = open(RAND_SOURCE, O_RDONLY);
+	if (rand_fd < 0) {
+		fprintf(stderr, "shred: %s is %s\n", RAND_SOURCE, strerror(errno));
+		return 1;
+	}
+
+	int zero_fd = open(ZERO_SOURCE, O_RDONLY);
+	if (zero_fd < 0) {
+		fprintf(stderr, "shred: %s is %s\n", ZERO_SOURCE, strerror(errno));
+		return 1;
+	}
+
+	for (; i < argc; i++) {
+		int fd = open(argv[i], O_WRONLY);
+		if (fd < 0) {
+			fprintf(stderr, "shred: %s is %s\n", argv[i], strerror(errno));
+			continue;
+		}
+
+		for (unsigned int n = 0; n <= n_loops; n++)
+			shred(rand_fd, zero_fd, fd, n);
+
+		close(fd);
+
+		if (u_flag)
+			if (unlink(argv[i]) < 0)
+				fprintf(stderr, "shred: %s is %s\n", argv[i], strerror(errno));
+
+		if (f_flag)
+			if (chmod(argv[i], 0) < 0)
+				fprintf(stderr, "shred: %s is %s\n", argv[i], strerror(errno));
+	}
+
+	close(rand_fd);
+	close(zero_fd);
+	return 0;
+}