File handling programs in C Programming

Example : Write a C program to copy the contents of one file to another file.

#include  
#include  		// For exit()
int main() 
{ 
    FILE *fp1, *fp2; 					// Declare two file pointer fp1 & fp2
    char filename[50], c; 
  
    printf("Enter the filename to open for reading "); 
    scanf("%s", filename); 
     
    fp1 = fopen(filename, "r");    			// Open file for read 
    if (fp1 == NULL) 
    { 
        printf("\n Cannot open file %s ", filename); 
        exit(0); 
    } 
  
    printf("\n Enter the filename to open for writing "); 
    scanf("%s", filename); 
       
    fp2 = fopen(filename, "w");      			 // Open file for write
    if (fp2 == NULL) 
    { 
        printf("\n Cannot open file %s", filename); 
        exit(0); 
    } 
   
   		 c = fgetc(fp1);        		 // Read contents from file
   		 while (c != EOF) 
   		 { 
      			  fputc(c, fp2);      	  // write character to another file
        			c = fgetc(fp1);   	 // Read contents from file
    		} 
      printf("\nContents copied to %s", filename); 
  
    fclose(fp1);      // closing file  
    fclose(fp2);      // closing file  
    return 0; 
}

OUTPUT

Enter the filename to open for reading
A.txt
Enter the filename to open for writing
B.txt
Contents copied to B.txt 

Example : Write a C program to appends the content of file at the end of another file.

Or

 Example : Write a C program to merge two files into third file.

#include 
#include 
int main()
{
    FILE *fp1, *fp2, *ftemp;
    char ch, file1[20], file2[20], file3[20];
 
    printf("Enter name of first file ");
    gets(file1);
    printf("\n Enter name of second file ");
    gets(file2);
    printf("\n Enter name to store merged file ");
    gets(file3);
   
    fp1 = fopen(file1, "r");
    fp2 = fopen(file2, "r");
   
    	 if (fp1 == NULL || fp2 == NULL)
    	{
      		  printf("\n Cannot open file "); 
      		  exit(0);
    	}

    ftemp = fopen(file3, "w");
  
  	if (ftemp == NULL)
    	{
         		printf("\n Cannot open file %s ", file3); 
        		exit(0);
    	}
    	while ((ch = fgetc(fp1)) != EOF)
        		fputc(ch, ftemp);
    	while ((ch = fgetc(fp2) ) != EOF)
        		fputc(ch, ftemp);
    
printf("\n Two files merged successfully in file =", file3);
    fclose(fp1);
    fclose(fp2);
    fclose(ftemp);
    return 0;
}

Enter name of first file
A.txt
Enter name of second file 
B.txt
Enter name to store merged file
Merge.txt
Two files merged successfully in file= Merge.txt

Example: Write a C program to count spaces ,vowels, consonants, digits in a file .

#include
#include
#include
#include
 
int main()
{
char ch, file1;
FILE *fp;
int  space,digit,vow,conso;
    
printf("Enter name of first file ");
gets(file1);
 
fp=fopen(file1,"a+");		// open a file in both read and write  mode
if(!fp)
 {
 printf("\n File Not Found =",file1);
 exit(0);
 }

space=digit=conso=vow=0;

while((ch=fgetc(fp))!=EOF)
{
 if(isspace(ch))
space++;
 
if(isdigit(ch))
digit++;

if(isalpha(ch))
  	 { 	switch(tolower(ch))
                	{
                                case 'a' : vow++;
                                                    break;
                                case 'e' : vow++;
                                                    break;
                                case 'i' : vow++;
                                                    break;
                                case 'o' : vow++;
                                                    break;
                                case 'u' : vow++;
                                                    break;
 
                      	        default    : conso++;
                                                    break;
               	 }
   	}
}
 
fflush(fp);
 
fprintf(fp,"\n No of vowels :   %d",vow);
fprintf(fp,"\n No of consonants : %d",conso);
fprintf (fp,"\n No of digits : %d",digit);
fprintf(fp,"\n No of white spaces : %d",space);
fclose(fpt);
 
getch();
 }

Enter name of first file

A.txt

No of vowels: 14

No of consonants: 45

No of digits: 4

No of white spaces: 23