Class 7: Homework

You must print this sheet out and write/type answers on it!

From your reading in APUE 7.3:
a) what is the minimum number of exit handlers guaranteed in ISO C to be supported?
```
      
```
b) how would you find out how many are supported on our machines?
```
      
```
Why won't the code given below compile:
```
#include <stdio.h>
#include <stdlib.h>

void foo(int x) { fprintf(stderr,"(%i) bye.\n",x); }

int main()
{
  atexit(foo);
  sleep(2);
  return 0;
}
      
```
BTW: compiling it to see what message is produced is a good thing, but you're going to have to explain why there's a problem here, so simply regurgitating the error message is not acceptable.
```
      
```

Compile and run each of these three programs (be patient when running them, they may take a minute to produce results):

p0.c

p1.c

p2.c

#include <stdio.h>
#include <stdlib.h>

int main()
{
  setvbuf(stdout,0,_IONBF,0);
  while(1)
  {
    int i;
    for(i = 0; i < 5; ++i)
    {
      sleep(1);
      fprintf(stdout,"%c",'X');
    }
    fprintf(stdout,"\n");    
  }
  return 0;
}

#include <stdio.h>
#include <stdlib.h>

int main()
{
  char B[12];
  setvbuf(stdout,B,_IOLBF,12);
  while(1)
  {
    int i;
    for(i = 0; i < 5; ++i)
    {
      sleep(1);
      fprintf(stdout,"%c",'X');
    }
    fprintf(stdout,"\n");    
   
  }
  return 0;
}

#include <stdio.h>
#include <stdlib.h>

int main()
{
  char B[64];
  setvbuf(stdout,B,_IOFBF,12);
  while(1)
  {
    int i;
    for(i = 0; i < 5; ++i)
    {
      sleep(1);
      fprintf(stdout,"%c",'X');
    }
    fprintf(stdout,"\n");    
   
  }
  return 0;
}

Explain explain what the output behvior is for each of the three programs, and explain thoroughly why they behave differently!