C Library Function – putc()

In C, the putc() function is used to write a character passed as an argument to a given stream. It is a standard library function defined in the <stdio.h> header file. The function first converts the character to unsigned char, then writes it to the given stream at the position indicated by the file pointer, and finally increments the file pointer by one.

Syntax of putc()

int putc(int ch, FILE *stream);

Parameters

• ch – This is the character to be written.
• stream – This is a pointer to a FILE object that identifies the stream where the character is to be written.

Return Value

• If the operation is successful, the function returns the character written.
• If an error occurs or the end of the file is reached, it returns EOF.

Examples of C putc() 

Example 1:

In this example, we will write a single character to a file using putc().

C

// C program to demonstrate the putc() function

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

int main()
{
    FILE* fp = NULL;
    // Open the file in write mode
    fp = fopen("C:\\Users\\General\\Desktop\\file.txt",
               "w");

    if (fp == NULL) {
        // Print an error message if
        // the file couldn't be opened
        printf("The file can't be opened!\n");
        // Exit the program with an error code
        exit(1);
    }
    // Character to be written to the file
    char ch = 'A';
    // Write the character to the file
    putc(ch, fp);
    // Print a message
    // indicating that
    // the file has
    // been modified
    printf("File has been modified !\n");
    // Close the file
    fclose(fp);
    // Set the file pointer to NULL for safety
    fp = NULL;

    return 0;
}

Output

File has been modified !

If we open the generated file.txt, it will print the following content:

C

// C program to display the content of the above text file

#include <stdio.h>

int main()
{
    FILE* fptr;
    int temp;
    // Open the file in read mode
    fptr = fopen("C:\\Users\\General\\Desktop\\file.txt",
                 "r");

    while (1) {
        // Read a character from the file
        temp = fgetc(fptr);
        // Check if end of file has been
        // reached
        if (feof(fptr)) {
            // If so, break out of the loop
            break;
        }

        // Print the character
        printf("%c", temp);
    }
    // Close the file
    fclose(fptr);

    return (0);
}

Output

A

Example 2:

In this example, we will use a for loop to write all the characters between A to Z to a file using putc(). See the following code:

C

// C program to demonstrate the putc() function

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

int main()
{
    FILE* fp = NULL;
    // Open the file in write mode
    fp = fopen("C:\\Users\\General\\Desktop\\file.txt",
               "w");

    if (fp == NULL) {
        // Print an error message if
        // the file couldn't be opened
        printf("The file can't be opened!\n");
        // Exit the program with an error code
        exit(1);
    }

    for (int ch = 65; ch <= 90; ch++) {
        // Write characters A to Z to the file
        putc(ch, fp);
    }
    // Print a message
    // indicating that
    // the file has
    // been modified

    printf("File has been modified !\n");
    // Close the file
    fclose(fp);
    // Set the file pointer to NULL for safety
    fp = NULL;

    return 0;
}

Output

File has been modified !

If we open the generated file.txt, it will print the following content:

C

// C program to display the content of the above text file

#include <stdio.h>

int main()
{
    FILE* fptr;
    int temp;
    // Open the file in read mode
    fptr = fopen("C:\\Users\\General\\Desktop\\file.txt",
                 "r");

    while (1) {
        // Read a character from the file
        temp = fgetc(fptr);
        // Check if end of file has been reached
        if (feof(fptr)) {
            // If so, break out of the loop
            break;
        }
        // Print the character
        printf("%c", temp);
    }
    // Close the file
    fclose(fptr);

    return (0);
}

Output

ABCDEFGHIJKLMNOPQRSTUVWXYZ