#include <stdio.h>
void fun(char * a)
{
    int i = 0, j = 0;
    while (a[i] == '*')
        i++;
    for (; a[i] != '\0'; i++, j++)
        a[j] = a[i];
    a[j] == '\0';
}
int main()
{
    char str[] = "123**aa";
    fun(str);
    printf("%s", str);
    return 0;
}

123**aa