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DUP
!!!DUP
NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
WARNING
CONFORMING TO
SEE ALSO
----
!!NAME


dup, dup2 - duplicate a file descriptor
!!SYNOPSIS


__#include
__ ''oldfd''__);
int dup2(int__ ''oldfd''__, int__ ''newfd''__);
__
!!DESCRIPTION


__dup__ and __dup2__ create a copy of the file
descriptor ''oldfd''.


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 __lseek__ 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.


__dup__ uses the lowest-numbered unused descriptor for
the new descriptor.


__dup2__ makes ''newfd'' be the copy of ''oldfd'',
closing ''newfd'' first if necessary.
!!RETURN VALUE


__dup__ and __dup2__ return the new descriptor, or -1
if an error occurred (in which case, ''errno'' is set
appropriately).
!!ERRORS


__EBADF__


''oldfd'' isn't an open file descriptor, or ''newfd''
is out of the allowed range for file
descriptors.


__EMFILE__


The process already has the maximum number of file
descriptors open and tried to open a new one.
!!WARNING


The error returned by __dup2__ is different to that
returned by __fcntl(__..., __F_DUPFD__, ...__)__
when ''newfd'' is out of range. On some systems
__dup2__ also sometimes returns __EINVAL__ like
__F_DUPFD__.
!!CONFORMING TO


SVr4, SVID, POSIX, X/OPEN, BSD 4.3. SVr4 documents
additional EINTR and ENOLINK error conditions. POSIX.1 adds
EINTR.
!!SEE ALSO


fcntl(2), open(2),
close(2)
----

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Version 1, saved on Tuesday, June 4, 2002 12:23:40 am by "perry"

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