31
There are several potential problems with this code.
First, it assumes a tty environment. That may be fine if
the assumption is true, but what if this code is called
from a GUI environment where neither stderr nor
stdin is open ?
Second, there is the problematic gets, which will write
as many characters as it receives into the buffer
passed in. Malicious users have used this failing to
create buffer overrun security holes in many different
systems. Never use gets().
Third, the code assumes the user understands English.
Finally, no one in their right mind would ever bury user
interaction such as this in a library routine

32
POSIX strcpy isn't guaranteed to work for
overlapping strings. It might happen to work on some
architectures, but only by coincidence

33
It won't work in an applet context with security
restrictions against writing to the local disk. Again,
when you have a choice of running in GUI contexts or
not, you may want to check dynamically to see what
the current environment is like. In this case, you may
want to put a log file somewhere other than the local
disk if it isn't accessible.