Module posix.fcntl
File Control.
Low-level control over file descriptors, including creating new file
descriptors with open.
| flock |
Advisory file locks. |
Functions
-
fcntl (fd, cmd[, arg=0])
-
Manipulate file descriptor.
Parameters:
- fd
int
file descriptor to act on
- cmd
int
operation to perform
- arg
int or flock
when cmd is
F_GETLK, F_SETLK or F_SETLKW,
then arg is a flock table, otherwise an integer with meaning dependent
upon the value of cmd.
(default 0)
Returns:
integer return value depending on cmd, if successful
Or
-
nil
-
string
error message
-
int
errnum
See also:
Usage:
local flag = P.fcntl (fd, P.F_GETFL)
-
open (path, oflags[, mode=511])
-
Open a file.
Parameters:
- path
string
- oflags
int
bitwise OR of zero or more of
O_RDONLY, O_WRONLY, O_RDWR,
O_APPEND, O_CREAT, O_DSYNC, O_EXCL, O_NOCTTY, O_NONBLOCK,
O_RSYNC, O_SYNC, O_TRUNC
- mode
int
access modes used by
O_CREAT
(default 511)
Returns:
int
file descriptor for path, if successful
Or
-
nil
-
string
error message
-
int
errnum
See also:
Usage:
fd = P.open ("data", bit.bor (P.O_CREAT, P.O_RDWR), bit.bor (P.S_IRWXU, P.S_IRGRP))
-
posix_fadvise (fd, offset, len, advice)
-
Instruct kernel on appropriate cache behaviour for a file or file segment.
Parameters:
- fd
int
open file descriptor
- offset
int
start of region
- len
int
number of bytes in region
- advice
int
one of
POSIX_FADV_NORMAL, POSIX_FADV_SEQUENTIAL,
POSIX_FADV_RANDOM, POSIX_FADV_NOREUSE, POSIX_FADV_WILLNEED or
POSIX_FADV_DONTNEED
Returns:
int
0, if successful
Or
-
nil
-
string
error message
-
int
errnum
See also:
Constants
-
posix.fcntl
-
Fcntl constants.
Any constants not available in the underlying system will be
nil valued.
Fields:
- F_DUPFD
int
duplicate file descriptor
- F_GETFD
int
get file descriptor flags
- F_SETFD
int
set file descriptor flags
- F_GETFL
int
get file status flags
- F_SETFL
int
set file status flags
- F_GETLK
int
get record locking information
- F_SETLK
int
set record locking information
- F_SETLKW
int
set lock, and wait if blocked
- F_GETOWN
int
get SIGIO/SIGURG process owner
- F_SETOWN
int
set SIGIO/SIGURG process owner
- F_RDLCK
int
shared or read lock
- F_WRLCK
int
exclusive or write lock
- F_UNLCK
int
unlock
- O_RDONLY
int
open for reading only
- O_WRONLY
int
open for writing only
- O_RDWR
int
open for reading and writing
- O_APPEND
int
set append mode
- O_CREAT
int
create if nonexistent
- O_DSYNC
int
synchronise io data integrity
- O_EXCL
int
error if file already exists
- O_NOCTTY
int
don't assign controlling terminal
- O_NONBLOCK
int
no delay
- O_RSYNC
int
synchronise file read integrity
- O_SYNC
int
synchronise file write integrity
- O_TRUNC
int
truncate to zero length
- POSIX_FADV_NORMAL
int
no advice
- POSIX_FADV_SEQUENTIAL
int
expecting to access data sequentially
- POSIX_FADV_RANDOM
int
expecting to access data randomly
- POSIX_FADV_NOREUSE
int
expecting to access data once only
- POSIX_FADV_WILLNEED
int
expecting to access data in the near future
- POSIX_FADV_DONTNEED
int
not expecting to access the data in the near future
Usage:
for name, value in pairs (require "posix.fcntl") do
if type (value) == "number" then
print (name, value)
end
end
Tables
-
flock
-
Advisory file locks.
Passed as arg to fcntl when cmd is
F_GETLK, F_SETLK or F_SETLKW.
Fields:
- l_start
int
starting offset
- l_len
int
len = 0 means until end of file
- l_pid
int
lock owner
- l_type
int
lock type
- l_whence
int
one of
SEEK_SET, SEEK_CUR or SEEK_END