fd_copy.3

linux下qmail的源码 本人加了一些注释

.TH fd_copy 3
.SH NAME
fd_copy \- duplicate a descriptor
.SH SYNTAX
.B #include <fd.h>

int \fBfd_copy\fP(\fIto\fR,\fIfrom\fR);

int \fIto\fR;
.br
int \fIfrom\fR;
.SH DESCRIPTION
.B fd_copy
copies 
descriptor
.I from
to descriptor
.IR to .
If
.I to
was already open,
.B fd_copy
closes it.
.B fd_copy
always leaves
.I from
intact;
if
.I to
and
.I from
are the same number,
.B fd_copy
does nothing.

.B fd_copy
returns 0 on success, -1 on error.
.B fd_copy
does not guarantee that
.I to
will remain open, if it was open, in case of error.
.SH "SEE ALSO"
dup(2),
fd_move(3)