John Regehr

@johnregehr stdin, stdout, stderr 0 1 2

@whitequark I know-- I'm asking why writing to stdin works

@whitequark actually writing to stdin does not work (on my system at least) but writing to fd 0 does work

@johnregehr oh, WRITING it's /dev/pts/1 opened guess konsole or getty opens it as O_RDWR.

@whitequark I just find it odd that this program prints 1 line instead of 0 or 2 http://pastebin.com/EpCQbqDg 

@johnregehr I guess FILE duplicates the open flags?

@johnregehr I could look at glibc or wherever in the kernel fds happen but you'd need to motivate me to do that

@johnregehr What is file descriptor 0 pointed at when this happens? I think I know the answer for the case it's a tty, but not otherwise.

@elwoz works the same when running "foo 0> output"

@johnregehr In that case you should be able to write *but not read* stdin. If you can read it, that's a bug in your shell.

@elwoz can definitely read and write fd 0 in the same process (on my mac)

@johnregehr If you can do that with "0>output", it's a bug in the shell.

@elwoz only works from console looks like

@johnregehr Isn't it the same as stdin? Why wouldn't writing to it work?

@ErrataRob but why should it work? should I also be able to read from stdout? where would the data that I get come from?

@johnregehr The other end of the pipe. I don't know, but I assume the shell does the standard create pipe for each one, then fork(3)

@ErrataRob when I write pipe code I always close the "wrong" ends -- maybe bash authors don't agree...

@johnregehr Write a test program that pipe/forks/execs another program that writes stdin and reads stdout....