Convert and count upper case and lowercase characters - c

Question

I am writing a C program to convert all uppercase characters to lowercase and all lowercase to uppercase from a file.
I also want to count the characters read and the number of characters converted to uppercase and characters converted to lowercase.
I am able to convert the characters but unable to figure out how to count them.
Example;
Hello World!
Output;
hELLO wORLD!
Read 13 characters in total.
8 converted to uppercase.
2 converted to lowercase.
Here's my code;
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#define INPUT_FILE "input.txt"
#define OUTPUT_FILE "output.txt"
int main()
{
FILE *inputFile = fopen(INPUT_FILE, "rt");
if (NULL == inputFile) {
printf("ERROR: cannot open the file: %s\n", INPUT_FILE);
return -1;
}
// 2. Open another file
FILE *outputFile = fopen(OUTPUT_FILE, "wt");
if (NULL == inputFile) {
printf("ERROR: cannot open the file: %s\n", OUTPUT_FILE);
return -1;
}
int c;
int ch;
int upper = 0;
int lower = 0;
int count = 0;
while (EOF != (c = fgetc(inputFile))) {
ch = islower(c)? toupper(c) : tolower(c);
fputc(ch, outputFile);
}
while (EOF != (c = fgetc(inputFile))) {
if (isupper(c))
{
upper++;
}
else if (islower(c))
{
lower++;
}
fputc(upper, outputFile);
fputc(lower, outputFile);
}
fclose(inputFile);
fclose(outputFile);
return 0;
}

Answer 1

Your main problem is that you are using 2 loops to read input file.
Your second loop should rewind the file before to start re-reading the file.
You can count and convert with a single loop.
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#define INPUT_FILE "input.txt"
#define OUTPUT_FILE "output.txt"
int main()
{
FILE *inputFile = fopen(INPUT_FILE, "rt");
if (NULL == inputFile) {
printf("ERROR: cannot open the file: %s\n", INPUT_FILE);
return -1;
}
// 2. Open another file
FILE *outputFile = fopen(OUTPUT_FILE, "w");
if (NULL == outputFile) {
printf("ERROR: cannot open the file: %s\n", OUTPUT_FILE);
return -1;
}
int ch;
int upper = 0;
int lower = 0;
int count = 0;
while (EOF != (ch = fgetc(inputFile)))
{
if (isalpha(ch))
{
if (islower(ch))
{
ch = toupper(ch);
upper++;
}
else
{
ch = tolower(ch);
lower++;
}
count++;
}
fputc(ch, outputFile);
}
fprintf(outputFile, "\nTotal: %d\nToUpper: %d\nToLower: %d\n", count, upper, lower);
fclose(inputFile);
fclose(outputFile);
return 0;
}
Take also note that you have to check if a read char is an alpha char before to convert the case, as the isalpha call inside the loop do.