added weekly exercises of isp-ws25

c/isp-ws25/weeklies/week09/w09ex02.c

@@ -0,0 +1,77 @@
+/*
+In this task, you should get familiar with file manipulation in C
+by performing operations like reading the file content,
+moving the file cursor, and writing the predefined string
+"Halftime is for the real fans" to a specific position in a file.
+
+Your tasks are:
+- Open file quote.txt in read/write mode
+  if fopen == NULL
+  - Print "Could not open file\n"
+  - return 1
+- Print original content of file to console
+- Ask user to enter a position to insert a predefined string
+- move cursor to the specified position
+  if cannot be moved
+  - Print "Could not move the file cursor\n"
+  - return 1
+- overwrite existing content (i.e. use fseek to move the cursor)
+- Write the predefined string into the file using fputs
+- Rewind the file to the beginning and print the updated content of the file to the console
+- Close the file properly after processing.
+
+Examples:
+
+Original file content: The first 90 minutes are the most important
+Position to insert the string: 4
+Updated file content: The Halftime is for the real fans important
+
+Original file content: The first 90 minutes are the most important
+Position to insert the string: -5
+Could not move the file cursor
+*/
+
+#include <stdio.h>
+
+int main(void)
+{
+  FILE *file = fopen("quote.txt", "r+");
+  if (NULL == file) {
+    printf("Could not open file\n");
+    return 1;
+  }
+
+  printf("Original file content: ");
+  int character = 0;
+  while ((character = fgetc(file)) != EOF)
+  {
+    printf("%c", character);
+  }
+  printf("\n");
+  rewind(file);
+
+  long insert_position = 0;
+  printf("Position to insert the string: ");
+  scanf("%ld", &insert_position);
+
+  if (fseek(file, insert_position, SEEK_CUR))
+  {
+    printf("Could not move the file cursor\n");
+    fclose(file);
+    return 1;
+  }
+  
+  char* text_to_insert = "Halftime is for the real fans";
+  fputs(text_to_insert, file);
+  rewind(file);
+
+  printf("Updated file content: ");
+  while ((character = fgetc(file)) != EOF)
+  {
+    printf("%c", character);
+  }
+  printf("\n");
+
+  fclose(file);
+  return 0;
+}