使用 sprintf_s() 后如何将 char* 重新转换为 integer？

Question

This is my casting from int to char*:

char* str = malloc(sizeof("0000"));
int int_ = 10;
sprintf_s(str, sizeof("0000"), "%04d", int_);
//str == "0010"

And I want to re-cast str to int back ( int_new == 10 ). How could I do this?

Answer 1

Use strlen to find the size of a string. Remember to add +1 for the nul byte at the end of the string. Otherwise, snprintf will fail.

int max_size = 5 ;
char* str = malloc(max_size);
int int_ = 10;
sprintf_s(str, max_size, "%04d", int_);

int int_new = atoi(str) ;

Alternative

int int_ = 10;

char buff[32] ;   // make it big enough to worst case
snprintf(buff, sizeof(buff), "%04d", int_) ;
char *str = strdup(buff) ;

int int_new = atoi(str) ;