luc086.c

Metadata

• Author — Amit Dutta
• Last updated — 08 Feb 2026
• License — MIT License (See the LICENSE file for details)

Problem Statement

Problem Statement

Write a program to copy contents of one file to another. While doing so replace all lowercase characters to their equivalent uppercase characters.

Source Code

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

void create_source_file();

int main()
{
    FILE *fs, *ft;
    char ch;

    create_source_file(); // Helper to make code runnable

    fs = fopen("source.txt", "r");
    if (fs == NULL)
    {
        printf("Cannot open source file.\n");
        exit(1);
    }

    ft = fopen("target.txt", "w");
    if (ft == NULL)
    {
        printf("Cannot open target file.\n");
        fclose(fs);
        exit(2);
    }

    while ((ch = fgetc(fs)) != EOF)
    {
        ch = toupper(ch);
        fputc(ch, ft);
    }

    printf("File copied successfully with uppercase conversion.\n");
    printf("Check 'target.txt' for results.\n");

    fclose(fs);
    fclose(ft);

    return 0;
}

void create_source_file()
{
    FILE *fp = fopen("source.txt", "w");
    if (fp)
    {
        fprintf(fp, "This is a sample text.\nIt contains Lowercase letters.\n");
        fclose(fp);
    }
}