dup2(3C) manual page
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dup2 - duplicate an open file descriptor
#include <unistd.h>
int dup2(int fildes, int fildes2);
Unsafe
Async-Signal-Safe
dup2() causes the file descriptor fildes2 to refer to the same file
as fildes. fildes is a file descriptor referring to an open file, and fildes2
is a non-negative integer less than the current value for the maximum number
of open file descriptors allowed the calling process (see getrlimit(2)
).
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.
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.
dup2()
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 dup2()
call.
- EMFILE
- the process has too many open files (see fcntl(2)
).
close(2)
,
creat(2)
, exec(2)
, fcntl(2)
, getrlimit(2)
, open(2)
, pipe(2)
, lockf(3C)
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