C Library Function – putc()

In C, the putc() function is used to write a character 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:

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.

Example 1: In this example, we will write a single character 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;

    fp = fopen("C:\\Users\\General\\Desktop\\file.txt",
               "w");

    if (fp == NULL) {
        printf("The file can't be opened!\n");
        exit(1);
    }

    char ch = 'A';

    putc(ch, fp);

    printf("File has been modified !\n");

    fclose(fp);

    fp = NULL;

    return 0;
}

Output

The 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 above txt file
#include <stdio.h>

int main()
{
    FILE* fptr;
    int temp;

    fptr = fopen("C:\\Users\\General\\Desktop\\file.txt",
                 "r");

    while (1) {
        temp = fgetc(fptr);
        if (feof(fptr)) {
            break;
        }
        printf("%c", temp);
    }
    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;

    fp = fopen("C:\\Users\\General\\Desktop\\file.txt",
               "w");

    if (fp == NULL) {
        printf("The file can't be opened!\n");
        exit(1);
    }

    for (int ch = 65; ch <= 90; ch++) {
        putc(ch, fp);
    }
    printf("File has been modified !\n");

    fclose(fp);

    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 above txt file
#include <stdio.h>

int main()
{
    FILE* fptr;
    int temp;

    fptr = fopen("C:\\Users\\General\\Desktop\\file.txt",
                 "r");

    while (1) {
        temp = fgetc(fptr);
        if (feof(fptr)) {
            break;
        }
        printf("%c", temp);
    }
    fclose(fptr);
    return (0);
}

Output

ABCDEFGHIJKLMNOPQRSTUVWXYZ