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dup 2 "28 Dec 1996" "SunOS 5.11" "System Calls"
NAME
dup - duplicate an open file descriptor
SYNOPSIS

#include <unistd.h>

int dup(int fildes);
DESCRIPTION

The dup() function returns a new file descriptor having the following in common with the original open file descriptor fildes:

same open file (or pipe)

same file pointer (that is, both file descriptors share one file pointer)

same access mode (read, write or read/write).

The new file descriptor is set to remain open across exec functions (see fcntl(2)).

The file descriptor returned is the lowest one available.

The dup(fildes) function call is equivalent to:

fcntl(fildes, F_DUPFD, 0)

RETURN VALUES

Upon successful completion, a non-negative integer representing the file descriptor is returned. Otherwise, -1 is returned and errno is set to indicate the error.

ERRORS

The dup() function will fail if:

EBADF

The fildes argument is not a valid open file descriptor.

EINTR

A signal was caught during the execution of the dup() function.

EMFILE

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

ENOLINK

The fildes argument is on a remote machine and the link to that machine is no longer active.

ATTRIBUTES

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPEATTRIBUTE VALUE
Interface StabilityStandard
MT-LevelAsync-Signal-Safe
SEE ALSO

close(2), creat(2), exec(2), fcntl(2), getrlimit(2), open(2), pipe(2), dup2(3C), lockf(3C), attributes(5), standards(5)