如何限制Char在C

Question

int main(void)
{
int studentnum = 2001041234;
char* firstname = "lux", * lastname = "ren", * middlename;

if (middlename)
{
    printf("%d-%s，%s", studentnum, lastname, firstname);
}
else
{
    fgets(middlename, 1, stdin);
    printf("%d-%s，%s%s", studentnum, lastname, firstname, middlename);
}
return 0;

}

我想限制middlename如果没有任何东西就是 printf("%d-%s，%s", studentnum, lastname, firstname);

如果有了那middlename只显示第一个字

我试过if (middlename = 0)但好像不能这样

Answer 1

middlename没有分配空间，下面代码都不行的，改为 char middlename[20] = {0};
if(middlename[0] = '\0') //表示middlename没东西
{
}
else
{
}