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dup(2)


dup -- duplicate an open file descriptor

Synopsis

   #include <unistd.h>
   

int dup(int fildes);

Description

dup duplicates an open file descriptor. fildes is a file descriptor obtained from a creat, open, dup, fcntl, pipe, or ioctl system call. dup returns a new file descriptor having the following in common with the original:

The new file descriptor is set to remain open across exec system calls [see fcntl(2)].

The file descriptor returned is the lowest one available.

Return values

On success, dup returns a non-negative integer, namely the file descriptor. On failure, dup returns -1 and sets errno to identify the error.

Errors

In the following conditions, dup fails and sets errno to:

EBADF
fildes is not a valid open file descriptor.

EINTR
A signal was caught during the dup system call.

EMFILE
The process has too many open files [see getrlimit(2)].

ENOLINK
fildes is on a remote machine and the link to that machine is no longer active.

References

close(2), creat(2), dup2(3C), exec(2), fcntl(2), getrlimit(2), lockf(3C), open(2), pipe(2)

Notices

Considerations for threads programming

Open file descriptors are a process resource and available to any sibling thread; if used concurrently, actions by one thread can interfere with those of a sibling.
© 2004 The SCO Group, Inc. All rights reserved.
UnixWare 7 Release 7.1.4 - 25 April 2004