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The functions in this section allow programs to allocate file
descriptors and pseudo-descriptors. A pseudo-descriptor is an
integer outside of the range of descriptors used by the kernel
(0..(OPEN_MAX - 1)
). Pseudo-descriptors are densely packed
(allocated sequentially beginning with OPEN_MAX
) and are suitable
for use with the function vu_set_fd_handler
(see A Virtual Unix File-System Interface).
int reserv (int * errn, int flags);
Allocate a file descriptor by opening "/dev/null"
by using
vu_open
in the manner descibed by flags
which may be one of
O_RDONLY
, O_RDWR
etc.
(See vu_open.)
int reserv_pseudo (int * errn, int flags);
Reserve a pseudo file descriptor suitable for use with
vu_set_fd_handler
. A pseudo file descriptor can be used with the
vu file system functions and is guaranteed not to be the same as
any real file descriptor. (see A Virtual Unix File-System Interface)
int reserv_pseudo_ge_n (int * errn, int n, int flags);
Reserve a pseudo file descriptor greater than or equal to n
suitable for use with vu_set_fd_handler
. A pseudo file
descriptor can be used with the vu file system functions and is
guaranteed not to be the same as any real file descriptor. (see
A Virtual Unix File-System Interface)
This function is useful for implementing vu_fcntl
with a cmd
argument F_DUPFD
.
void unreserv_pseudo (int fd);
Release a pseudo-descriptor previously allocated by
reserved_pseudo
.
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