Simple C Programs Based On File Handling.

**Program which replaces a particular character in the file with another character. In case the character repeats then only the last occurrence is replaced.**

#include<stdio.h>

#include<conio.h>

int main()

{

    FILE *fp;

    int pos;    //Opening the file in the write mode.

    fp=fopen("srecord.txt","w");

    if(fp==NULL)

    printf("\nError");

    char str[]="Sample String in a File";

    char c,c1,c2;  //Writing to the file using fputs

    fputs(str,fp);

    fflush(fp);

    printf("\nEnter character you want to search");

    scanf("%c",&c1);

    printf("\nEnter character you want to modify");

    fflush(stdin);

    scanf("%c",&c2);   //Taking the file pointer to the beginning of the file

    rewind(fp);   //Reading the file character by character till the EOF.

    while((fscanf(fp,"%c",&c))!=EOF)

    {

    //Store the position with the match

    if(c==c1)

    pos=ftell(fp)-1;

    }

    //Take the file pointer to the beginning.

    rewind(fp);   //Position the file pointer at the replacement point

    fseek(fp,pos,0);     //Printing other character at its place

    fprintf(fp,"%c",c2);   //Taking the pointer to the beginning

    rewind(fp);

    printf("\nContents of the file are ");   //Printing the contents on the screen

    while((fscanf(fp,"%s",str))!=EOF)

    printf("%s ",str);    

    fclose(fp);    //Closing the file.

    getch();

}    

Program 2: Reading and writing data in to the file using structure.

#include<stdio.h>

#include<conio.h>

#include<stdlib.h>  //Creating structure

struct student

{

char name[20];

int rollno;

float marks;

};

void Write();

void Read();  

FILE *fp;   //File stream pointer

int count;

//Structure Variable which will be read and written

struct student s1;

int main()

{

int ch;

while(1)

{

printf("\n1.Write Data");

printf("\n2.Read Data");

printf("\n3.Exit");

printf("\nChoice");

scanf("%d",&ch);

if(ch==1)

{

Write();

}

if(ch==2)

{

Read();

}

if(ch==3)

exit(0);

}

}

void Write()

{

count++;

//Open the file in a+ mode so as to read and write data to the file

fp=fopen("K1201.txt","a+");

printf("\nName:- ");

fflush(stdin);

gets(s1.name);

printf("\nRoll Number:- ");

scanf("%d",&s1.rollno);

printf("\nMarks:- ");

scanf("%f",&s1.marks);

//Use the fwrite function to write the data to the file

fwrite(&s1,sizeof(struct student),1,fp);

//Close the file after writing the data

fclose(fp);

}

void Read()

{

int i;

//Open the file in a+ mode so that we can read and write the data

fp=fopen("K1201.txt","a+");

for(i=0;i<count;i++)

{

//Read all the records from the file one by one. We are reading an entire

//structure variable one at a time

fread(&s1,sizeof(struct student),1,fp);

printf("\nName:- %s",s1.name);

printf("\nRoll Number:- %d",s1.rollno);

printf("\nMarks:- %f",s1.marks);

}

//Closing the file

fclose(fp);

}

From site : http://ctechrockz.blogspot.com/