dup, dup2 - duplicate a file descriptor
int dup(int oldfd);
int dup2(int oldfd, int newfd);
create a copy of the file descriptor
After successful return of dup or dup2,
the old and new descriptors may be used interchangeably. They share
locks, file position pointers and flags; for example, if the file
position is modified by using
on one of the descriptors, the position is also changed for the other.
The two descriptors do not share the close-on-exec flag, however.
uses the lowest-numbered unused descriptor for the new descriptor.
makes newfd be the copy of oldfd, closing newfd
first if necessary.
return the new descriptor, or -1 if an error occurred (in which case,
is set appropriately).
isn't an open file descriptor, or
is out of the allowed range for file descriptors.
The process already has the maximum number of file
descriptors open and tried to open a new one.
call was interrupted by a signal.
(Linux only) This may be returned by
during a race condition with open() and dup().
The error returned by
is different from that returned by
is out of range. On some systems
also sometimes returns
was open, any errors that would have been reported at
time, are lost. A careful programmer will not use
SVr4, SVID, POSIX, X/OPEN, BSD 4.3. SVr4 documents additional
EINTR and ENOLINK error conditions. POSIX.1 adds EINTR.
The EBUSY return is Linux-specific.
- RETURN VALUE
- CONFORMING TO
- SEE ALSO