C Write Text File

Summary: in this tutorial, you will learn how to write a text file using C standard library functions.

Steps for writing to a text file

To write to a text file, you follow these steps:

• First, open the text file for writing using fopen() function with the "w" mode.
• Second, write a text to the text file using the fprintf() function.
• Third, close the file using the fclose() function.

It is important to note that if you use the “w” mode, the fopen() will delete all contents of the file if the file exists.

C Write Text File Example

The following program illustrates how to use the fprintf() function to write to a text file:

#include <stdio.h>

int main()
{
    char *filename = "test.txt";

    // open the file for writing
    FILE *fp = fopen(filename, "w");
    if (fp == NULL)
    {
        printf("Error opening the file %s", filename);
        return -1;
    }
    // write to the text file
    for (int i = 0; i < 10; i++)
        fprintf(fp, "This is the line #%d\n", i + 1);

    // close the file
    fclose(fp);

    return 0;
}
Code language: C++ (cpp)

Write to a text file using the fputc() function

To write a character to a text file, you use the fputc() function. The following program shows how to use the fputc() function to write to a text file:

#include <stdio.h>

int main()
{
    char *filename = "alphabet.txt";

    // open the file for writing
    FILE *fp = fopen(filename, "w");
    if (fp == NULL)
    {
        printf("Error opening the file %s", filename);
        return -1;
    }
    // write to the text file
    for (char ch = 'a'; ch < 'z'; ch++)
        fputc(ch, fp);

    // close the file
    fclose(fp);

    return 0;
}
Code language: PHP (php)

The program writes the characters from a to z to the alphabet.txt file. If you execute the program and open the alphabet.txt file, you’ll see the following content:

abcdefghijklmnopqrstuvwxy

Summary

• Use the fprintf() function to write a line of text to the text file.
• Use the fputc() function to write a single character to a file.