File operations – Theory and Programs [Learn to code]

What are File operations? Different modes of File operations and programs on File operations.

• 098. Write a program to read and write a file character by character.

  #include<stdio.h>
  int main()
  {
      FILE *fp;   /* file pointer*/
      char fName;
      char ch;
   
      printf("\nEnter file name to create :");
      scanf("%s",fName);
   
      fp = fopen(fName,"w");
      if(fp==NULL)
      {
          printf("File not created !!");
          exit(0); 
      }
   
      printf("File created successfully.");
      /*writing into file*/
      printf("\nEnter text to write (press < enter > to save & quit):\n");
      while( (ch = getchar())!='\n')
      {
          putc(ch, fp); /*write character into file*/
      }
  
  /*again open file to read data*/
      fp = fopen(fName,"r");
      if(fp==NULL)
      {
          printf("\nCan't open the file!!!");
          exit(0);
      }
   
      printf("\nContents of file is :\n");
      /*read text until, end of file is not detected*/
      while( (ch=getc(fp))!=EOF )
      {
          printf("%c",ch); /*print character on screen*/
      }
   
      fclose(fp);
      return 0;
  }
  

• 099. Write a program to read and write a file line by line.

  #include<stdio.h>
  int main()
  {
      FILE *fp;
      char str;
      fp = fopen("C:\\myfile.txt", "w");
  
      if (fp == NULL)
      {
         puts("An error occurred while opening the specified file");
      }
  
       printf("Enter your string:");
  
       gets(str);
  
       fputs(str, fp);
  
       fclose(fp);
  
      fp = fopen("C:\\myfile.txt", "r");
  
      if (fp == NULL)
      {
         puts("An error occurred while opening the specified file");
      }
  
      while(1)
      {
         if(fgets(str, 10, fp) ==NULL)
              break;
         else
              printf("%s", str);
      }
  
      fclose(fp);
      return 0;
  }
  

• 100. Merge two files by store data into third one

  #include<stdio.h>
  #include<stdlib.h>
  
  int main()
  {
     FILE *fp1 = fopen("file1.txt", "r");
  
     FILE *fp2 = fopen("file2.txt", "r");
  
     FILE *fp3 = fopen("file3.txt", "w");
  
     char c;
     if (fp1 == NULL || fp2 == NULL || fp3 == NULL)
     {
           puts("Could not open files");
           exit(0);
     }
  
     while ((c = fgetc(fp1)) != EOF)
        fputc(c, fp3);
  
     while ((c = fgetc(fp2)) != EOF)
        fputc(c, fp3);
  
     fclose(fp1);
     fclose(fp2);
     fclose(fp3);
     return 0;
  }