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.TH FD 4
.CT 2 file_io
.SH NAME
fd, stdin, stdout, stderr, tty \- file descriptor files
.SH DESCRIPTION
These files, conventionally called
.BR /dev/fd/\^0 ", " /dev/fd/1 ", ... " /dev/fd/127 ,
refer to files accessible through file descriptors.
If file descriptor
.I n
is open,
these two system calls have the same effect:
.IP
.EX
fd = open("/dev/fd/\fIn\fP", mode);
fd = dup(\fIn\fP\^);
.EE
.LP
On these devices
.I creat
(see
.IR open (2))
is equivalent to
.I open,
and
.I mode
is ignored.
As with
.IR dup ,
subsequent reads or writes on
.I fd
fail unless the original file descriptor
allows the operations.
.SH FILES
.TF /dev/stdout
.TP
.F /dev/fd/*
.TP
.F /dev/stdin
linked to
.F /dev/fd/0
.TP
.F /dev/stdout
linked to
.F /dev/fd/1
.TP
.F /dev/stderr
linked to
.F /dev/fd/2
.TP
.F /dev/tty
linked to
.F /dev/fd/3
.SH SEE ALSO
.IR open (2),
.IR dup (2)
.SH DIAGNOSTICS
.I Open
returns \-1
and
.B EBADF
if the related file descriptor is not open
and in the appropriate mode (reading or writing).
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