/*
 * C Program to Convert the Content of File to LowerCase
 */
#include <stdio.h>
#include <errno.h>

int to_lower_file(FILE *);

void main(int argc, char * argv[])
{
    int op = -1;
    char ch;
    FILE *fp;
    if (fp = fopen(argv[1], "r+"))
        {
            printf("FILE has been opened..!!!\n");
            op = to_lower_file(fp);
            printf(" %d \n", op);
            fclose(fp);
        }
    else
        {
            perror("Error Occured");
            printf(" %d\n ", op);
        }
}

int to_lower_file(FILE *f)
{
    int c;
    char ch;
    while ((ch = fgetc(f))! = EOF)
        {
            c = (int)ch;
            if (c >= 65 && c <= 90)
                {
                    ch = ch + 32;
                    fseek(f, -1L, 1);
                    fputc(ch, f);
                }
        }
    return 0;
}