NAME

dup2 − duplicate an open file descriptor

SYNOPSIS

#include <unistd.h>

int dup2 (int fildes, int fildes2);

DESCRIPTION

fildes is a file descriptor referring to an open file, and fildes2 is a non-negative integer less than {OPEN_MAX} (the maximum number of open files).  dup2 causes fildes2 to refer to the same file as fildes.  If fildes2 already referred to an open file, not fildes, it is closed first.  If fildes2 refers to fildes, or if fildes is not a valid open file descriptor, fildes2 will not be closed first. 

dup2 will fail if one or more of the following are true:

EBADF fildes is not a valid open file descriptor. 

EBADF fildes2 is negative or greater than or equal to {OPEN_MAX}. 

EINTR a signal was caught during the dup2 call. 

EMFILE {OPEN_MAX} file descriptors are currently open. 

SEE ALSO

creat(2), close(2), exec(2), fcntl(2), open(2), pipe(2), lockf(3C), limits(4)

DIAGNOSTICS

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.