Beispiele 19.10.2023

20231019/arrays-05a.c

+#include <stdio.h>
+
+int main (void)
+{
+  int prime[6] = { 2, 3, 5, 0, 7, 11 };
+  for (int *p = prime; *p; p++)
+    printf ("%d\n", *p);
+  return 0;
+}

20231019/arrays-05b.c

+#include <stdio.h>
+
+int main (void)
+{
+  int prime[5] = { 2, 3, 5, 7, 11 };
+  for (int *p = prime; *p; p++)
+    printf ("%d\n", *p);
+  return 0;
+}

20231019/arrays-05c.c

+
+#include <stdio.h>
+
+int main (void)
+{
+  int pflll[8] = { 1, 2, 3, 4, 5, 6, 7, 8 };
+  int prime[8] = { 2, 3, 5, 7, 11, 13, 17, 19 };
+  printf ("prime:\n");
+  for (int *p = prime; *p; p++)
+    printf ("%d\n", *p);
+  printf ("pflll:\n");
+  for (int *q = pflll; *q; q++)
+    printf ("%d\n", *q);
+  return 0;
+}

20231019/fhello.txt

+Hello, world!

20231019/files-01.c

+#include <stdio.h>
+
+int main (void)
+{
+  FILE *f = fopen ("fhello.txt", "w");
+  fprintf (f, "Hello, world!\n");
+  fclose (f);
+  return 0;
+}

20231019/files-02.c

+#include <stdio.h>
+
+int main (void)
+{
+  FILE *f = fopen ("fhello.txt", "w");
+  if (f)
+    {
+      fprintf (f, "Hello, world!\n");
+      fclose (f);
+    }
+  return 0;
+}

20231019/files-03.c

+#include <stdio.h>
+
+int main (void)
+{
+  FILE *f = fopen ("fhello.txt", "w");
+  if (f)
+    {
+      fprintf (f, "Hello, world!\n");
+      fclose (f);
+    }
+  else
+    printf ("Fehlermeld!\n");
+  return 0;
+}

20231019/files-04.c

+#include <stdio.h>
+
+int main (void)
+{
+  FILE *f = fopen ("fhello.txt", "w");
+  if (f)
+    {
+      fprintf (f, "Hello, world!\n");
+      fclose (f);
+    }
+  else
+    fprintf (stderr, "Fehlermeld!\n");
+  return 0;
+}

20231019/files-05.c

+#include <stdio.h>
+#include <errno.h>
+
+int main (void)
+{
+  FILE *f = fopen ("fhello.txt", "w");
+  if (f)
+    {
+      fprintf (f, "Hello, world!\n");
+      fclose (f);
+    }
+  else
+    fprintf (stderr, "Fehler Nr. %d\n", errno);
+  return 0;
+}

20231019/files-06.c

+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+
+int main (void)
+{
+  FILE *f = fopen ("fhello.txt", "w");
+  if (f)
+    {
+      fprintf (f, "Hello, world!\n");
+      fclose (f);
+    }
+  else
+    {
+      char *msg = strerror (errno);
+      fprintf (stderr, "Fehler: %s\n", msg);
+    }
+  return 0;
+}

20231019/files-07.c

+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+
+int main (void)
+{
+  FILE *f = fopen ("fhello.txt", "w");
+  if (f)
+    {
+      fprintf (f, "Hello, world!\n");
+      fclose (f);
+      return 0;
+    }
+  else
+    {
+      char *msg = strerror (errno);
+      fprintf (stderr, "Fehler: %s\n", msg);
+      return errno;
+    }
+}

20231019/files-07.txt

+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+
+int main (void)
+{
+  FILE *f = fopen ("fhello.txt", "w");
+  if (f)
+    {
+      fprintf (f, "Hello, world!\n");
+      fclose (f);
+      return 0;
+    }
+  else
+    {
+      char *msg = strerror (errno);
+      fprintf (stderr, "Fehler: %s\n", msg);
+      return errno;
+    }
+}
+cassini/home/peter/bo/2023ws/hp/20231019> gcc -Wall -O files-07.c -o files-07
+cassini/home/peter/bo/2023ws/hp/20231019> ./files-07
+Fehler: Permission denied
+cassini/home/peter/bo/2023ws/hp/20231019> echo $?
+13
+cassini/home/peter/bo/2023ws/hp/20231019> rm fhello.txt
+rm: reguläre Datei (schreibgeschützt) 'fhello.txt' entfernen? y
+cassini/home/peter/bo/2023ws/hp/20231019> ./files-07
+cassini/home/peter/bo/2023ws/hp/20231019> echo $?
+0
+cassini/home/peter/bo/2023ws/hp/20231019> ls -l fhello.txt
+-rw-r--r-- 1 peter peter 14 19. Okt 15:56 fhello.txt
+cassini/home/peter/bo/2023ws/hp/20231019> chmod -w fhello.txt
+cassini/home/peter/bo/2023ws/hp/20231019> ls -l fhello.txt
+-r--r--r-- 1 peter peter 14 19. Okt 15:56 fhello.txt
+cassini/home/peter/bo/2023ws/hp/20231019> ./files-07
+Fehler: Permission denied
+cassini/home/peter/bo/2023ws/hp/20231019> echo $?
+13
+cassini/home/peter/bo/2023ws/hp/20231019>

20231019/files-08.c

+#include <stdio.h>
+#include <errno.h>
+#include <error.h>
+
+int main (void)
+{
+  FILE *f = fopen ("fhello.txt", "w");
+  if (!f)
+    error (errno, errno, "cannot open file");
+  fprintf (f, "Hello, world!\n");
+  fclose (f);
+  return 0;
+}

20231019/params-00.c

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

20231019/params-01.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;
+}

20231019/params-02.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;
+}

20231019/params-03.c

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

20231019/side-effects-16.c

+#include <stdio.h>
+
+void add_verbose (int a, int b)
+{
+  printf ("%d + %d = %d\n", a, b, a + b);
+}
+
+int main (void)
+{
+  add_verbose (3, 7);
+  return 0;
+}

20231019/side-effects-17.c

+#include <stdio.h>
+
+int add_verbose (int a, int b)
+{
+  printf ("%d + %d = %d\n", a, b, a + b);
+}
+
+int main (void)
+{
+  add_verbose (3, 7);
+  return 0;
+}

20231019/side-effects-18.c

+#include <stdio.h>
+
+int add_verbose (int a, int b)
+{
+  printf ("%d + %d = %d\n", a, b, a + b);
+  return 42;
+}
+
+int main (void)
+{
+  add_verbose (3, 7);
+  return 0;
+}