C Programming | File Handling | Terminal-based Development

Introduction

In this lab, you will learn how to create a new file in C programming language and write data to it. The FILE data type is used to represent a file in C, and the fopen() function is used to open a file for reading, writing, or appending. Once a file is opened, data can be written to it using the fprintf() function, and the fclose() function is used to close the file after writing data.

Create a new C program using the terminal

Open the terminal and create a new C program called main.c in the ~/project/ directory using the command:

nano ~/project/main.c

In the main.c file, include the necessary header files:

#include <stdio.h>
#include <stdlib.h>

Define variables and pointers

Define variables and pointer of type FILE to hold the file and its content:

FILE *fptr;
char name[20];
int age;
float salary;

Open a file for writing

Open a file for writing using the fopen() function. If the file does not exist, it will be created. Otherwise, its contents will be overwritten:

fptr = fopen("emp.txt", "w");
if (fptr == NULL)
{
    printf("File does not exist.\n");
    return 1;
}

Write data to the file

Ask the user to enter the employee's name, age, and salary, and write it to the file using the fprintf() function:

printf("Enter the name:\n");
scanf("%s", name);
fprintf(fptr, "Name  = %s\n", name);

printf("Enter the age:\n");
scanf("%d", &age);
fprintf(fptr, "Age  = %d\n", age);

printf("Enter the salary:\n");
scanf("%f", &salary);
fprintf(fptr, "Salary  = %.2f\n", salary);

Close the file

Close the file using the fclose() function:

fclose(fptr);

Complete the code

#include <stdio.h>
#include <stdlib.h>

int main() {
    FILE *fptr;
    char name[20];
    int age;
    float salary;

    // open for writing
    fptr = fopen("emp.txt", "w");
    if (fptr == NULL) {
        printf("File does not exist.\n");
        return 1;
    }

    printf("Enter the name:\n");
    scanf("%s", name);
    fprintf(fptr, "Name  = %s\n", name);

    printf("Enter the age:\n");
    scanf("%d", &age);
    fprintf(fptr, "Age  = %d\n", age);

    printf("Enter the salary:\n");
    scanf("%f", &salary);
    fprintf(fptr, "Salary  = %.2f\n", salary);

    fclose(fptr);
    return 0;
}

Summary

In this lab, you have learned how to create a new file in C programming language and write data to it using the FILE, fopen(), fprintf(), and fclose() functions. Remember to always close the file after writing data to it to avoid data loss.

Create and Write to C Files