README.txt
-- Mark Claypool, claypool@cs.wpi.edu


OVERVIEW

This code is designed to test whether file descriptors above 0, 1 and
2 are closed after an exec() call.

fd.c - opens a file, then execs() fd2.  The file descriptor should be
3.

fd2.c - writes to file descriptor 3.  If it works, it should indicate
it has printed a message.  Otherwise, it will report an error.


HYPOTHESIS

It is expected that all file descriptors remain open after an exec(),
although it is possible that only the "main" descriptors do so (0, 1,
2) since those are the only open ones upon an initial shell process
creation.


RESULT

claypool 178 carbon=>>ls
fd*  fd2*  fd2.c  fd.c  Makefile  README.txt
claypool 179 carbon=>>fd2
write: Bad file descriptor
claypool 180 carbon=>>fd
Child said: Hello, world!
claypool 181 carbon=>>ls
fd*  fd2*  fd2.c  fd.c  file.txt  Makefile  README.txt
claypool 182 carbon=>>cat file.txt
Hello, world!


CONCLUSION

The success message by the child indicates that file descriptors above
2 are *not* closed after an exec().