Beispiele und Screenshots 7.11.2024

20241107/fhello.txt

+Hello, world!

20241107/files-01.c

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

20241107/files-01.txt

+#include <stdio.h>
+
+int main (void)
+{
+  FILE *f = fopen ("fhello.txt", "w");
+  fprintf (f, "Hello, world!\n");
+  fclose (f);
+  return 0;
+}
+cassini/home/peter/bo/2024ws/hp/20241107> gcc -Wall -O3 files-01.c -o files-01
+cassini/home/peter/bo/2024ws/hp/20241107> ./files-01
+cassini/home/peter/bo/2024ws/hp/20241107> cat fhello.txt
+Hello, world!
+cassini/home/peter/bo/2024ws/hp/20241107> ls -l fhello.txt
+-rw-r--r-- 1 peter peter 14  7. Nov 12:40 fhello.txt
+cassini/home/peter/bo/2024ws/hp/20241107> chmod 000 fhello.txt
+cassini/home/peter/bo/2024ws/hp/20241107> ls -l fhello.txt
+---------- 1 peter peter 14  7. Nov 12:40 fhello.txt
+cassini/home/peter/bo/2024ws/hp/20241107> ./files-01
+Speicherzugriffsfehler
+cassini/home/peter/bo/2024ws/hp/20241107>

20241107/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;
+}

20241107/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 ("Fehler!\n");
+  return 0;
+}

20241107/files-04.c

+#include <stdio.h>
+
+int main (void)
+{
+  FILE *f = fopen ("fhello.txt", "w");
+  if (f)
+    {
+      fprintf (f, "Hello, world!\n");
+      fclose (f);
+      return 0;
+    }
+  else
+    {
+      fprintf (stderr, "Fehler!\n");
+      return 1;
+    }
+}

20241107/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);
+      return 0;
+    }
+  else
+    {
+      fprintf (stderr, "Fehler Nr. %d!\n", errno);
+      return 1;
+    }
+}

20241107/files-06.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);
+      return 0;
+    }
+  else
+    {
+      fprintf (stderr, "err#%d!\n", errno);
+      return 1;
+    }
+}

20241107/files-07.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);
+      return 0;
+    }
+  else
+    {
+      fprintf (stderr, "err#%d!\n", errno);
+      return errno;
+    }
+}

20241107/files-08.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, "%s\n", msg);
+      return errno;
+    }
+}

20241107/files-09.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;
+}

20241107/main-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;
+}

20241107/main-params-02.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;
+}

20241107/main-params-03.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;
+}

20241107/string-ops-01.c

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

20241107/string-ops-02.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));
+
+  return 0;
+
+  hello[5] = 0;
+  printf ("%s\n", hello);
+  printf ("%zd\n", strlen (hello));
+
+  return 0;
+}

20241107/string-ops-03.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;
+}

20241107/string-ops-04.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));
+
+  printf ("%s\n", hello + 6);
+  printf ("%zd\n", strlen (hello + 6));
+
+  return 0;
+}

20241107/strings-10.c

+#include <stdio.h>
+
+int main (void)
+{
+  char *hello = "Hello, world!\n";
+  printf ("%s", p);
+  return 0;
+}

20241107/strings-11.c

+#include <stdio.h>
+
+int main (void)
+{
+  char *hello = "Hello, world!\n";
+  printf ("%s", *p);
+  return 0;
+}