You are permitted, and encouraged, to work together on these problems,
provided that every contributor understands how the complete solution
was found. Put the names of all contributors into comments at the top of
your C file:

   /* assignment 7 */
   /* Joe Bloggs */
   /* Alice Smith */

Your solutions are due Friday 19 October at 17:00. Send each C file in
a separate email message to djb-275-hw@cr.yp.to:

   mail djb-275-hw@cr.yp.to < ex7.c
   mail djb-275-hw@cr.yp.to < ex8.c

You are permitted to use standard C library functions in these problems.


7. Write a copy program that, given command-line arguments f1 and f2,
copies the contents of the file named f1 to a new file named f2. For
example,

   copy dyn3.c ex5.c

will create a new file named ex5.c with the same contents as the
existing file named dyn3.c.

If f2 already exists, your program must wipe out the previous contents
of f2. If your program has any trouble reading f1 or writing f2, it must
print an error message on stderr and exit.


8. Write a merge program that, given command-line arguments f1 and f2,
reads lines from files f1 and f2, and prints the lines in lexicographic
order.

You may assume that the lines in f1 are already in order, and that the
lines in f2 are already in order. You may also assume that each line
consists entirely of lowercase letters followed by a newline. If these
assumptions are violated, your program is permitted to produce strange
output (for example, lines out of order), but it must not crash.

For example, if f1 contains
   aardvark
   hello
   two
and f2 contains
   food
   fried
   less
then your program will print
   aardvark
   food
   fried
   hello
   less
   two
in that order.

The amount of memory used by your program must be proportional to the
size of the longest line of input.

If your program has any trouble reading f1, reading f2, or allocating
memory, it must print an error message on stderr and exit.