Reversing array logic in C not working properly - c

Question

I am trying to read the input to my program (a string of chars) and invert the order of the words that are in it.
For example, if I were to pass my program ABC DEF GHI JKL it would output JKL GHI DEF ABC. I am using the whitespace as separators.
My code:
char toReverse[1000];
char outputArray[1000];
int charCount = //Size of the toReverse array. Varies on the input
//It is the total number of chars stored in the array
...
int i;
int tempCharCount = charCount;
int wordSize = 0;
int outputIndex = 0;
int sentenceIndex = 0;
int charStep = 0;
for(i = charCount-1; i>=0; i--){
if(toReverse[i] == ' '){
int j;
sentenceIndex = tempCharCount - wordSize;
for(j = 0; j<charStep; j++){
outputArray[outputIndex++] = toReverse[sentenceIndex++];
}
outputArray[outputIndex] = ' ';
outputIndex++;
charStep = 0;
}
wordSize++;
charStep++;
}
There is a flaw in my code. I do know why this happens though. For example, if I were to pass as input ABC DEF GHI, it will only output GHI DEF. This is because whenever the outer for loop reaches index 0 of my toReverse array, since it is not a space ' ', it does not do the if(toReverse[i]) inner for(j = 0; j<charStep; j++) since the condition is not met.
Do you have any advice regarding to the logic? I have tried reversing my logic, such as if(toReverse[i] != ' ') but it brings more problems than it solves.
Thanks for your advice and comments!
Cheers
Edit 1
I am reading my input from a file By the way!
Update 1
Here I am basically trying to open various files and read chars from them
int main(int argc, char * argv[])
{
int i = 1;
FILE * fp = NULL;
if(1==argc){
do_read(stdin);
}else{
// cycle through all files in command line arguments and read them
for (i=1; i < argc; i++) {
if ((fp = fopen(argv[i], "r")) == NULL) {
printf("Failed to open file.\n");
}
else {
do_read(fp);
fclose(fp);
}
}
}
//printf("\n");
//printf("\n");
printf("%i",charCount);
return 0;
}

Answer 1

sample
#include <stdio.h>
#include <string.h>
void proc_rev(char toReverse[], char outputArray[]){
int charCount = strlen(toReverse);
int i;
int tempCharCount = charCount;
int wordSize = 0;
int outputIndex = 0;
int sentenceIndex = 0;
int charStep = 0;
for(i = charCount-1; i>=0; i--){
if(toReverse[i] == ' '){
int j;
sentenceIndex = tempCharCount - wordSize;
for(j = 0; j<charStep; j++){
outputArray[outputIndex++] = toReverse[sentenceIndex++];
}
outputArray[outputIndex] = ' ';
outputIndex++;
charStep = 0;
}
wordSize++;
charStep++;
}
outputArray[outputIndex] = '\0';
}
int main(void){
FILE *fp = stdin;
char toReverse[1000] = " ";
char outputArray[1000];
while(1 == fscanf(fp, "%998[^\n]%*c", &toReverse[1])){
proc_rev(toReverse, outputArray);
puts(outputArray);
}
return 0;
}
void do_read(FILE *fp){
char toReverse[1000] = " ";
char outputArray[1000];
while(1 == fscanf(fp, "%998[^\n]%*c", &toReverse[1])){
proc_rev(toReverse, outputArray);
puts(outputArray);
}
}

Answer 2

This code is not tested but basic idea is reversing the whole string once and then reverse it word by word. idea is correct, implementation may have bugs
void swap(char* s, int i, int j) {
char tmp = s[i];
s[i] = s[j];
s[j] = tmp;
}
void rev(char* stirng, int start, int len) {
for (int i=0; i<len/2; ++i) {
swap(string, i, len-i-1);
}
}
int main() {
char* string = read from file
int len = strlen(string);
rev(string, 0, len);
for (int i=0; i<len;) {
int l = 0;
int j=i;
while (j<len && string[j]!=' ') ++j;
rev(string, i, j-i);
i=j+1;
}
}

Answer 3

The current logic reverses individual words from last to second word. However to reverse the first word you will have to add a check apart from
if(toReverse[i] == ' ')
as the first character need not be a space.
A separate check can be used when counter 'i' reaches zero, i.e. first character