DEVFD
Section: Devices and Network Interfaces (4)
Updated: 5 December 1995
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NAME
/dev/fd/#, /dev/stdin, /dev/stdout, /dev/stderr - file descriptor files
SYNOPSIS
pseudo-device devfd15
DESCRIPTION
The files
/dev/fd/0
through
/dev/fd/15
refer to file descriptors which can be accessed through the file
system.
We are limited to File Descriptor 15 because of a Kernel Bug in NeXTSTEP 3.3
which causes a panic when `/usr/etc/mknod /dev/fd/16 c 1 16' is performed
(don't try this at home kiddys).
The driver can accept up to descriptor 255 if you wish to risk making your
own nodes, or wish to expand the limit in the PostLoader.
If the file descriptor is open and the mode the file is being opened
with is a subset of the mode of the existing descriptor, the call:
fd = open("/dev/fd/n", mode);
and the call:
fd = fcntl(n, F_DUPFD, 0);
are equivalent.
Opening the files
/dev/stdin ,
/dev/stdout
and
/dev/stderr
is equivalent to the following calls:
fd = fcntl(0, F_DUPFD, 0);
fd = fcntl(1, F_DUPFD, 0);
fd = fcntl(2, F_DUPFD, 0);
Flags to the
open(2)
call other than
O_RDONLY ,
O_WRONLY
and
O_RDWR
are ignored.
FILES
/dev/fd/#
/dev/stdin
/dev/stdout
/dev/stderr
SEE ALSO
tty(4)
DIAGNOSTICS
/dev/fd/n: Bad file number
File descriptor
n
wasn't open before trying to open /dev/fd/n.
/dev/fd/n: Permission denied
Requested mode isn't a subset of the mode of the existing descriptor.
HISTORY
Derived from the /dev/fd driver written for V7 UNIX I wrote in a previous life.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- FILES
-
- SEE ALSO
-
- DIAGNOSTICS
-
- HISTORY
-
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