Beispiele und Tafelbilder 8.11.2021

20211108/blink-0.c

+#include <avr/io.h>
+
+int main (void)
+{
+  DDRD = 0x40;   /* binär: 0100 0000 */
+  PORTD = 0x40;  /* binär: 0100 0000 */
+  while (1);
+  return 0;
+}

20211108/blink-1.c

+#include <avr/io.h>
+
+#define F_CPU 16000000l
+#include <util/delay.h>
+
+int main (void)
+{
+  DDRD = 0x01;
+  PORTD |= 0x01;
+  while (1)
+    {
+      _delay_ms (500);
+      PORTD &= ~0x01;
+      _delay_ms (500);
+      PORTD |= 0x01;
+    }
+  return 0;
+}

20211108/blink-3.c

+#include <avr/io.h>
+
+#define F_CPU 16000000
+#include <util/delay.h>
+
+int main (void)
+{
+  DDRD = 0x01;
+  PORTD = 0x01;
+  while (1)
+    {
+      while ((PIND & 0x02) == 0)
+        ; /* just wait */
+      PORTD ^= 0x01;
+    }
+  return 0;
+}

20211108/exploit-1.c

+#include <stdio.h>
+#include <stdlib.h>
+
+int main (void)
+{
+  char name[42];
+  printf ("Ihr Name: ");
+  fflush (stdout);
+  fgets (name, 42, stdin);
+  char buffer[100];
+  snprintf (buffer, 100, "echo \"Hallo, %s!\"", name);
+  system (buffer);
+  return 0;
+}

20211108/exploit-1.txt

+cassini/home/peter/bo/2021ws/hp/20211108> ./exploit-1
+Ihr Name: Peter $(ls -lrt | tail -4)
+Hallo, Peter -rw-r--r-- 1 peter peter     82 Nov  8 13:28 hello.c
+-rwxr-xr-x 1 peter peter  16608 Nov  8 13:28 hello
+-rw-r--r-- 1 peter peter    254 Nov  8 13:32 exploit-1.c
+-rwxr-xr-x 1 peter peter  16888 Nov  8 13:32 exploit-1
+!
+cassini/home/peter/bo/2021ws/hp/20211108>

20211108/main-params-1.c

+#include <stdio.h>
+
+int main (int argc, char **argv)
+{
+  printf ("argc = %d\n", argc);
+  for (int i = 0; i < argc; i++)
+    printf ("argv[%d] = \"%s\"\n", i, argv[i]);
+  return 0;
+}

20211108/main-params-2.c

+#include <stdio.h>
+
+int main (int argc, char **argv)
+{
+  printf ("argc = %d\n", argc);
+  for (int i = 0; argv[i]; i++)
+    printf ("argv[%d] = \"%s\"\n", i, argv[i]);
+  return 0;
+}

20211108/main-params-3.c

+#include <stdio.h>
+
+int main (int argc, char **argv)
+{
+  printf ("argc = %d\n", argc);
+  int i = 0;
+  while (*argv)
+    printf ("argv[%d] = \"%s\"\n", i++, *argv++);
+  return 0;
+}

20211108/main-params-4.c

+#include <stdio.h>
+
+void remove_first_parameter (int argc, char **argv)
+{
+  argc--;
+  argv++;
+}
+
+int main (int argc, char **argv)
+{
+  remove_first_parameter (argc, argv);
+  printf ("argc = %d\n", argc);
+  int i = 0;
+  while (*argv)
+    printf ("argv[%d] = \"%s\"\n", i++, *argv++);
+  return 0;
+}

20211108/main-params-5.c

+#include <stdio.h>
+
+void remove_first_parameter (int *argc, char ***argv)
+{
+  *argc--;
+  *argv++;
+}
+
+int main (int argc, char **argv)
+{
+  remove_first_parameter (&argc, &argv);
+  printf ("argc = %d\n", argc);
+  int i = 0;
+  while (*argv)
+    printf ("argv[%d] = \"%s\"\n", i++, *argv++);
+  return 0;
+}

20211108/main-params-6.c

+#include <stdio.h>
+
+void remove_first_parameter (int *argc, char ***argv)
+{
+  (*argc)--;
+  (*argv)++;
+}
+
+int main (int argc, char **argv)
+{
+  remove_first_parameter (&argc, &argv);
+  printf ("argc = %d\n", argc);
+  int i = 0;
+  while (*argv)
+    printf ("argv[%d] = \"%s\"\n", i++, *argv++);
+  return 0;
+}

20211108/string-ops-1.c

+#include <stdio.h>
+#include <string.h>
+
+int main (void)
+{
+  char hello[] = "Hello, world!\n";
+
+  printf ("%s\n", hello);
+  printf ("%zd\n", strlen (hello));
+
+  printf ("%s\n", hello + 7);
+  printf ("%zd\n", strlen (hello + 7));
+
+  hello[5] = 0;
+  printf ("%s\n", hello);
+  printf ("%zd\n", strlen (hello));
+
+  return 0;
+}

20211108/string-ops-10.c

+#include <stdio.h>
+#include <string.h>
+
+int main (void)
+{
+  char buffer[100] = "";
+  snprintf (buffer, 100, "Die Antwort lautet: %d", 42);
+  printf ("%s\n", buffer);
+
+  char *answer = strstr (buffer, "Antwort");
+  printf ("%s\n", answer);
+  printf ("found at: %zd\n", answer - buffer);
+
+  return 0;
+}

20211108/string-ops-2.c

+#include <stdio.h>
+#include <string.h>
+
+int main (void)
+{
+  char *anton = "Anton";
+  char *klein_anton = "anton";
+  char *zacharias = "Zacharias";
+
+  printf ("%d\n", strcmp (klein_anton, zacharias));
+  printf ("%d\n", strcmp (zacharias, klein_anton));
+  printf ("%d\n", strcmp (klein_anton, klein_anton));
+
+  char buffer[100] = "Huber ";
+  strncat (buffer, anton, 99);
+  printf ("%s\n", buffer);
+
+  return 0;
+}

20211108/string-ops-3.c

+#include <stdio.h>
+#include <string.h>
+
+int main (void)
+{
+  char *anton = "Anton";
+  char *zacharias = "Zacharias";
+
+  if (anton < zacharias)
+    printf ("%s vor %s\n", anton, zacharias);
+  else if (anton > zacharias)
+    printf ("%s nach %s\n", anton, zacharias);
+  else
+    printf ("%s = %s\n", anton, zacharias);
+
+  return 0;
+}

20211108/string-ops-4.c

+#include <stdio.h>
+#include <string.h>
+
+int main (void)
+{
+  char *zacharias = "Zacharias";
+  char *anton = "Anton";
+
+  if (anton < zacharias)
+    printf ("%s vor %s\n", anton, zacharias);
+  else if (anton > zacharias)
+    printf ("%s nach %s\n", anton, zacharias);
+  else
+    printf ("%s = %s\n", anton, zacharias);
+
+  return 0;
+}

20211108/string-ops-5.c

+#include <stdio.h>
+#include <string.h>
+
+char *zacharias = "Zacharias";
+char *anton = "Anton";
+
+int main (void)
+{
+  if (anton < zacharias)
+    printf ("%s vor %s\n", anton, zacharias);
+  else if (anton > zacharias)
+    printf ("%s nach %s\n", anton, zacharias);
+  else
+    printf ("%s = %s\n", anton, zacharias);
+  return 0;
+}

20211108/string-ops-6.c

+#include <stdio.h>
+#include <string.h>
+
+char *anton = "Anton";
+char *zacharias = "Zacharias";
+
+int main (void)
+{
+  if (anton < zacharias)
+    printf ("%s vor %s\n", anton, zacharias);
+  else if (anton > zacharias)
+    printf ("%s nach %s\n", anton, zacharias);
+  else
+    printf ("%s = %s\n", anton, zacharias);
+  return 0;
+}

20211108/string-ops-7.c

+#include <stdio.h>
+#include <string.h>
+
+int main (void)
+{
+  char *huber_anton = "Huber" " " "Anton";
+  printf ("%s\n", huber_anton);
+  return 0;
+}