Unix Programming - Re: Need help with piping

Author

Re: Need help with piping

William Ahern

2004-11-19, 5:51 pm

Fletcher Glenn <fletcher@removethisfoglight.com> wrote:
> Before you can use a file descriptor as a dup2 target, you must close it
> if it is open. In the case of zero and one, these descriptors are open.

From dup(2) on Linux:

dup2 makes newfd be the copy of oldfd, closing newfd first if
necessary.

From dup(2) on OpenBSD

In dup2(), the value of the new descriptor newd is specified. If
this descriptor is already in use, it is first deallocated as if a
close(2) call had been done first.