Convert string to int c code example

Example 1: string to int c

atoi(str) is unsafe

This is the prefered method:
(int)strtol(str, (char **)NULL, 10)

Example 2: convert stirng to int c++

int thing = std::stoi(string);

Example 3: c convert char to int

int i = (int)(c - '0');

Example 4: how to cast string to int in c

use atoi from the stdlib.h 
char *string = "hi";
int x = atoi(string);