dup2

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    DUP(2)              Linux Programmer's Manual              DUP(2)

    NAME
           dup, dup2 - duplicate a file descriptor

    SYNOPSIS
           #include <unistd.h>

           int dup(int oldfd);
           int dup2(int oldfd, int newfd);

    DESCRIPTION
           dup and dup2 create a copy of the file descriptor oldfd.

           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
           SVID, AT&T, POSIX, X/OPEN, BSD 4.3

### SEE ALSO

fcntl, open,

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    Linux 1.1.46              21 August 1994                        1

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