NAME

dup − duplicate an open file descriptor

SYNOPSIS

#include <unistd.h>

int dup(int fildes);

MT-LEVEL

Async-Signal-Safe

DESCRIPTION

dup() 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) is equivalent to

fcntl( fildes, F_DUPFD, 0 )

RETURN VALUES

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

ERRORS

dup() will fail if one or more of the following are true:

EBADF fildes is not a valid open file descriptor. 

EINTR A signal was caught during the dup() function. 

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ENOLINK fildes is on a remote machine and the link to that machine is no longer active. 

SEE ALSO

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

SunOS 5.5  —  Last change: 23 Feb 1993