Weitere Beispielprogramme 31.10.2019

20191031/files-1.c

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

20191031/files-2.c

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

20191031/files-3.c

+#include <stdio.h>
+
+int main (void)
+{
+  FILE *f = fopen ("c:\\windows\\system\\kern64.dll", "w");
+  fprintf (f, "Hello, world!\n");
+  fclose (f);
+  return 0;
+}

20191031/files-4.c

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

20191031/files-5.c

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

20191031/files-6.c

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

20191031/files-7.c

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

20191031/files-8.c

+#include <stdio.h>
+#include <errno.h>
+#include <error.h>
+
+int main (void)
+{
+  FILE *f = fopen ("/etc/passwd", "w");
+  if (!f)
+    error (1, errno, "cannot open file");
+  fprintf (f, "Hello, world!\n");
+  fclose (f);
+  return 0;
+}

20191031/files-9.c

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

20191031/strings-10.c

+#include <stdio.h>
+
+int main (void)
+{
+  volatile char answer[] = {42, 137, 13, 117};
+  char *a = answer;
+  char hello[14] = "Hello, world!\n";
+  printf ("%s", hello);
+  a -= 4;
+  printf ("a: %d %d %d %d %d %d %d %d\n", a[0], a[1], a[2], a[3], a[4], a[5], a[6], a[7]);
+  return 0;
+}

20191031/strings-11.c

+#include <stdio.h>
+
+int main (void)
+{
+  volatile char answer[] = {42, 65, 66, 117};
+  char *a = answer;
+  char hello[14] = "Hello, world!\n";
+  printf ("%s", hello);
+  a -= 4;
+  printf ("a: %d %d %d %d %d %d %d %d\n", a[0], a[1], a[2], a[3], a[4], a[5], a[6], a[7]);
+  return 0;
+}

20191031/strings-6.s

+	.file	"strings-6.c"
+	.section	.rodata.str1.1,"aMS",@progbits,1
+.LC0:
+	.string	"%s"
+.LC1:
+	.string	"Answer: %d\n"
+	.text
+	.globl	main
+	.type	main, @function
+main:
+.LFB11:
+	.cfi_startproc
+	subq	$40, %rsp
+	.cfi_def_cfa_offset 48
+	movl	$1963821354, 28(%rsp)
+	movabsq	$8583909746840200520, %rax
+	movq	%rax, 14(%rsp)
+	movl	$1684828783, 22(%rsp)
+	movw	$2593, 26(%rsp)
+	leaq	14(%rsp), %rsi
+	leaq	.LC0(%rip), %rdi
+	movl	$0, %eax
+	call	printf@PLT
+	movzbl	28(%rsp), %esi
+	movsbl	%sil, %esi
+	leaq	.LC1(%rip), %rdi
+	movl	$0, %eax
+	call	printf@PLT
+	movl	$0, %eax
+	addq	$40, %rsp
+	.cfi_def_cfa_offset 8
+	ret
+	.cfi_endproc
+.LFE11:
+	.size	main, .-main
+	.ident	"GCC: (Debian 6.3.0-18+deb9u1) 6.3.0 20170516"
+	.section	.note.GNU-stack,"",@progbits

20191031/strings-7.s

+	.file	"strings-7.c"
+	.section	.rodata.str1.1,"aMS",@progbits,1
+.LC0:
+	.string	"%s"
+.LC1:
+	.string	"Answer: %d\n"
+	.text
+	.globl	main
+	.type	main, @function
+main:
+.LFB11:
+	.cfi_startproc
+	subq	$40, %rsp
+	.cfi_def_cfa_offset 48
+	movabsq	$8506888665401493802, %rax
+	movq	%rax, 24(%rsp)
+	movabsq	$8583909746840200520, %rax
+	movq	%rax, 10(%rsp)
+	movl	$1684828783, 18(%rsp)
+	movw	$2593, 22(%rsp)
+	leaq	10(%rsp), %rsi
+	leaq	.LC0(%rip), %rdi
+	movl	$0, %eax
+	call	printf@PLT
+	movzbl	24(%rsp), %esi
+	movsbl	%sil, %esi
+	leaq	.LC1(%rip), %rdi
+	movl	$0, %eax
+	call	printf@PLT
+	movl	$0, %eax
+	addq	$40, %rsp
+	.cfi_def_cfa_offset 8
+	ret
+	.cfi_endproc
+.LFE11:
+	.size	main, .-main
+	.ident	"GCC: (Debian 6.3.0-18+deb9u1) 6.3.0 20170516"
+	.section	.note.GNU-stack,"",@progbits

20191031/strings-8.c

+#include <stdio.h>
+
+int main (void)
+{
+  volatile char answer[] = {42, 137, 13, 117};
+  char hello[14] = "Hello, world!\n";
+  printf ("%s", hello);
+  printf ("Answer: %d %d %d %d\n", answer[0], answer[1], answer[2], answer[3]);
+  return 0;
+}

20191031/strings-9.c

+#include <stdio.h>
+
+int main (void)
+{
+  volatile char answer[] = {42, 137, 13, 117};
+  char *a = answer;
+  char hello[14] = "Hello, world!\n";
+  printf ("%s", hello);
+  printf ("Answer: %d %d %d %d\n", answer[0], answer[1], answer[2], answer[3]);
+  a -= 4;
+  printf ("a: %d %d %d %d\n", a[0], a[1], a[2], a[3]);
+  return 0;
+}

20191031/structs-1.c

+#include <stdio.h>
+
+typedef struct
+{
+  char day, month;
+  int year;
+}
+date;
+
+void set_date (date *d)
+{
+  (*d).day = 31;
+  (*d).month = 10;
+  (*d).year = 2019;
+}
+
+int main (void)
+{
+  date today;
+  set_date (&today);
+  printf ("%d.%d.%d\n", today.day, today.month, today.year);
+  return 0;
+}

20191031/structs-2.c

+#include <stdio.h>
+
+typedef struct
+{
+  char day, month;
+  int year;
+}
+date;
+
+void set_date (date *d)
+{
+  (*d).day = 31;
+  (*d).month = 10;
+  (*d).year = 2019;
+}
+
+void print_date (date *d)
+{
+  printf ("%d.%d.%d\n", (*d).day, (*d).month, (*d).year);
+}
+
+int main (void)
+{
+  date today;
+  set_date (&today);
+  print_date (&today);
+  return 0;
+}

20191031/structs-3.c

+#include <stdio.h>
+
+typedef struct
+{
+  char day, month;
+  int year;
+}
+date;
+
+void set_date (date *d)
+{
+  d->day = 31;
+  d->month = 10;
+  d->year = 2019;
+}
+
+void print_date (date *d)
+{
+  printf ("%d.%d.%d\n", d->day, d->month, d->year);
+}
+
+int main (void)
+{
+  date today;
+  set_date (&today);
+  print_date (&today);
+  return 0;
+}