C trying to copy pointer to a new pointer - c

Question

I need help with a couple of things:
I'm trying to delete a word from a pointer and put it in a new pointer with a new length but i am not able to copy it to the new pointer
I'm not sure when should I use the free() function.
when I use the free(str) in the delete function it crashes.
After I copy the "str" to the "newStr" what is the best way to copy the "newStr" back to the "str" with the new length?
Please help me understand it, I'm new with this and I googled it, I tried looking here and didn't find something that could help me.
void delete(char *str)
{
int i, indexStart = 0, indexEnd = 0, wordlen = 0, newLen = 0, len = 0;
printf("Enter the index of the word that you want to remove: ");
scanf("%d", &i);
indexs(i, str,&indexStart,&indexEnd,&wordlen);
len = strlen(str);
newLen = len - wordlen - 1;
char *newStr = (char*)malloc(newLen * sizeof(char));
if (newStr == NULL)
{
printf("Error! memory not allocated.");
exit(0);
}
for (int j = 0; j < len; j++)
{
if (j< (indexStart - 1) || j > indexEnd)
{
*newStr = *str;
newStr++;
}
str++;
}
free(str);
//free(newStr);
printf("The new string: %s\n", newStr);
}
void main()
{
char *str = (char*)malloc(1 * sizeof(char));
if (str == NULL)
{
printf("Error! memory not allocated.");
exit(0);
}
text(str);
if (str != NULL)
{
delete(str);
}
free(str);
system("pause");
}

Answer 1

According to the structured programming paradigm your functions should solve small separate tasks. But your function delete() prints to the console, scans input, allocates new string and fills this new string. But what's event worse is the call exit() in this function. If something went wrong, function must to return an error, but not to stop the program. Also names of functions should relfect what they do.
Use free() for every memory block allocated by malloc().
So, this is a working code:
#include <stddef.h>
#include <stdio.h>
#include <string.h>
#include <malloc.h>
const char *findWord(const char *str, const char *delimiters, unsigned index) {
// validate input parameters
if (!str || !delimiters) {
return NULL;
}
// count words
unsigned count = 0;
while (*str && count < index) {
// skip delimiters
while (*str && !strchr(delimiters, *str)) {
str++;
}
if (*str) {
count++;
}
// skip word
while (*str && strchr(delimiters, *str)) {
str++;
}
}
// if index is too big returns NULL
return *str ? str : NULL;
}
unsigned countLengthOfWord(const char *str, const char *delimiters) {
// validate input parameters
if (!str || !delimiters) {
return 0;
}
// count length
unsigned length = 0;
while (*str && !strchr(delimiters, *str++)) {
length++;
}
return length;
}
char *cutWord(char *str, const char *delimiters, unsigned index) {
// validate input parameters
if (!str) {
return NULL;
}
str = (char *)findWord(str, delimiters, index);
// if index is too big, return NULL
if (!str) {
return NULL;
}
// allocate new string for word
unsigned length = countLengthOfWord(str, delimiters);
char *word = malloc(length + 1);
// check if allocation was successfull
if (!word) {
return NULL;
}
// copy word
strncpy(word, str, length);
word[length] = '\0';
// cut word from string
const char *ptr = str + length;
while (*ptr) {
*str++ = *ptr++;
}
*str = '\0';
return word;
}
int main() {
char str1[] = "Hello, my world!";
char str2[] = "Hello, my world!";
char str3[] = "Hello, my world!";
char *word1 = cutWord(str1, " ,!", 0);
char *word2 = cutWord(str2, " ,!", 1);
char *word3 = cutWord(str3, " ,!", 2);
if (word1) {
printf("word: %s\nstring: %s\n\n", word1, str1);
}
if (word2) {
printf("word: %s\nstring: %s\n\n", word2, str2);
}
if (word3) {
printf("word: %s\nstring: %s\n\n", word3, str3);
}
// release allocated memory
free(word1);
free(word2);
free(word3);
getchar();
return 0;
}