Module: File::Constants
Relationships & Source Files | |
Extension / Inclusion / Inheritance Descendants | |
Included In:
| |
Defined in: | file.c |
Overview
Module Constants
defines file-related constants.
There are two families of constants here:
-
Those having to do with
file access
. -
Those having to do with
filename globbing
.
File constants defined for the local process may be retrieved with method File::Constants.constants
:
File::Constants.constants.take(5)
# => [:RDONLY, :WRONLY, :RDWR, :APPEND, :CREAT]
File Access
File-access constants may be used with optional argument mode
in calls to the following methods:
Read/Write Access
Read-write access for a stream may be specified by a file-access constant.
The constant may be specified as part of a bitwise OR of other such constants.
Any combination of the constants in this section may be specified.
File::RDONLY
Flag File::RDONLY
specifies the stream should be opened for reading only:
filepath = '/tmp/t.tmp'
f = File.new(filepath, File::RDONLY)
f.write('Foo') # Raises IOError (not opened for writing).
File::WRONLY
Flag File::WRONLY
specifies that the stream should be opened for writing only:
f = File.new(filepath, File::WRONLY)
f.read # Raises IOError (not opened for reading).
File::RDWR
Flag File::RDWR
specifies that the stream should be opened for both reading and writing:
f = File.new(filepath, File::RDWR)
f.write('Foo') # => 3
f.rewind # => 0
f.read # => "Foo"
File Positioning
File::APPEND
Flag File::APPEND
specifies that the stream should be opened in append mode.
Before each write operation, the position is set to end-of-stream. The modification of the position and the following write operation are performed as a single atomic step.
File::TRUNC
Flag File::TRUNC
specifies that the stream should be truncated at its beginning. If the file exists and is successfully opened for writing, it is to be truncated to position zero; its ctime and mtime are updated.
There is no effect on a FIFO special file or a terminal device. The effect on other file types is implementation-defined. The result of using File::TRUNC
with File::RDONLY
is undefined.
Creating and Preserving
File::CREAT
Flag File::CREAT
specifies that the stream should be created if it does not already exist.
If the file exists:
- Raise an exception if File::EXCL is also specified.
- Otherwise, do nothing.
If the file does not exist, then it is created. Upon successful completion, the atime, ctime, and mtime of the file are updated, and the ctime and mtime of the parent directory are updated.
File::EXCL
Flag File::EXCL
specifies that the stream should not already exist; If flags File::CREAT
and File::EXCL
are both specified and the stream already exists, an exception is raised.
The check for the existence and creation of the file is performed as an atomic operation.
If both File::EXCL
and File::CREAT
are specified and the path names a symbolic link, an exception is raised regardless of the contents of the symbolic link.
If File::EXCL
is specified and File::CREAT
is not specified, the result is undefined.
POSIX File Constants
Some file-access constants are defined only on POSIX-compliant systems; those are:
-
File::SYNC
. -
File::DSYNC
. -
File::RSYNC
. -
File::DIRECT
. -
File::NOATIME
. -
File::NOCTTY
. -
File::NOFOLLOW
. -
File::TMPFILE
.
File::SYNC
, File::RSYNC
, and File::DSYNC
Flag File::SYNC
, File::RSYNC
, or File::DSYNC
specifies synchronization of I/O operations with the underlying file system.
These flags are valid only for POSIX-compliant systems.
-
File::SYNC
specifies that all write operations (both data and metadata) are immediately to be flushed to the underlying storage device. This means that the data is written to the storage device, and the file’s metadata (e.g., file size, timestamps, permissions) are also synchronized. This guarantees that data is safely stored on the storage medium before returning control to the calling program. This flag can have a significant impact on performance since it requires synchronous writes, which can be slower compared to asynchronous writes. -
File::RSYNC
specifies that any read operations on the file will not return until all outstanding write operations (those that have been issued but not completed) are also synchronized. This is useful when you want to read the most up-to-date data, which may still be in the process of being written. -
File::DSYNC
specifies that all data write operations are immediately to be flushed to the underlying storage device; this differs from File::SYNC, which requires that metadata also be synchronized.
Note that the behavior of these flags may vary slightly depending on the operating system and filesystem being used. Additionally, using these flags can have an impact on performance due to the synchronous nature of the I/O operations, so they should be used judiciously, especially in performance-critical applications.
File::NOCTTY
Flag File::NOCTTY
specifies that if the stream is a terminal device, that device does not become the controlling terminal for the process.
Defined only for POSIX-compliant systems.
File::DIRECT
Flag File::DIRECT
requests that cache effects of the I/O to and from the stream be minimized.
Defined only for POSIX-compliant systems.
File::NOATIME
Flag File::NOATIME
specifies that act of opening the stream should not modify its access time (atime).
Defined only for POSIX-compliant systems.
File::NOFOLLOW
Flag File::NOFOLLOW
specifies that if path is a symbolic link, it should not be followed.
Defined only for POSIX-compliant systems.
File::TMPFILE
Flag File::TMPFILE
specifies that the opened stream should be a new temporary file.
Defined only for POSIX-compliant systems.
Other File-Access Constants
File::NONBLOCK
When possible, the file is opened in nonblocking mode. Neither the open operation nor any subsequent I/O operations on the file will cause the calling process to wait.
File::BINARY
Flag File::BINARY
specifies that the stream is to be accessed in binary mode.
File::SHARE_DELETE
Flag File::SHARE_DELETE
enables other processes to open the stream with delete access.
Windows only.
If the stream is opened for (local) delete access without File::SHARE_DELETE
, and another process attempts to open it with delete access, the attempt fails and the stream is not opened for that process.
Locking
Four file constants relate to stream locking; see #flock:
File::LOCK_EX
Flag File::LOCK_EX
specifies an exclusive lock; only one process a a time may lock the stream.
File::LOCK_NB
Flag File::LOCK_NB
specifies non-blocking locking for the stream; may be combined with File::LOCK_EX
or File::LOCK_SH
.
File::LOCK_SH
Flag File::LOCK_SH
specifies that multiple processes may lock the stream at the same time.
File::LOCK_UN
Flag File::LOCK_UN
specifies that the stream is not to be locked.
Filename Globbing Constants (File::FNM_*)
Filename-globbing constants may be used with optional argument flags
in calls to the following methods:
The constants are:
File::FNM_CASEFOLD
Flag File::FNM_CASEFOLD
makes patterns case insensitive for fnmatch (but not Dir.glob).
File::FNM_DOTMATCH
Flag File::FNM_DOTMATCH
makes the '*'
pattern match a filename starting with '.'
.
File::FNM_EXTGLOB
Flag File::FNM_EXTGLOB
enables pattern '{a,b}'
, which matches pattern ‘a’ and pattern ‘b’; behaves like a regexp union (e.g., '(?:a|b)'
):
pattern = '{LEGAL,BSDL}'
Dir.glob(pattern) # => ["LEGAL", "BSDL"]
Pathname.glob(pattern) # => [#<Pathname:LEGAL>, #<Pathname:BSDL>]
pathname.glob(pattern) # => [#<Pathname:LEGAL>, #<Pathname:BSDL>]
File::FNM_NOESCAPE
Flag File::FNM_NOESCAPE
disables '\'
escaping.
File::FNM_PATHNAME
Flag File::FNM_PATHNAME
specifies that patterns '*'
and '?'
do not match the directory separator (the value of constant SEPARATOR).
File::FNM_SHORTNAME
Flag File::FNM_SHORTNAME
allows patterns to match short names if they exist.
Windows only.
File::FNM_SYSCASE
Flag File::FNM_SYSCASE
specifies that case sensitivity is the same as in the underlying operating system; effective for fnmatch, but not Dir.glob.
Other Constants
File::NULL
Flag File::NULL
contains the string value of the null device:
-
On a Unix-like OS,
'/dev/null'
. -
On Windows,
'NUL'
.
Constant Summary
-
APPEND =
:APPEND}[File::Constants@File-3A-3AAPPEND]
{File
-
BINARY =
:BINARY}[File::Constants@File-3A-3ABINARY]
{File
-
CREAT =
:CREAT}[File::Constants@File-3A-3ACREAT]
{File
-
DIRECT =
:DIRECT}[File::Constants@File-3A-3ADIRECT]
{File
-
DSYNC =
:DSYNC}[File::Constants@File-3A-3ASYNC-2C+File-3A-3ARSYNC-2C+and+File-3A-3ADSYNC]
{File
-
EXCL =
:EXCL}[File::Constants@File-3A-3AEXCL]
{File
-
LOCK_EX =
:LOCK_EX}[File::Constants@File-3A-3ALOCK_EX]
{File
-
LOCK_NB =
:LOCK_NB}[File::Constants@File-3A-3ALOCK_NB]
{File
-
LOCK_SH =
:LOCK_SH}[File::Constants@File-3A-3ALOCK_SH]
{File
-
LOCK_UN =
:LOCK_UN}[File::Constants@File-3A-3ALOCK_UN]
{File
-
NOATIME =
Linux
INT2FIX(O_NOATIME)
-
NOCTTY =
:NOCTTY}[File::Constants@File-3A-3ANOCTTY]
{File
-
NOFOLLOW =
FreeBSD, Linux
INT2FIX(O_NOFOLLOW)
-
NONBLOCK =
:NONBLOCK}[File::Constants@File-3A-3ANONBLOCK]
{File
-
NULL =
:NULL}[File::Constants@File-3A-3ANULL]
{File
-
RDONLY =
:RDONLY}[File::Constants@File-3A-3ARDONLY]
{File
-
RDWR =
:RDWR}[File::Constants@File-3A-3ARDWR]
{File
-
RSYNC =
:RSYNC}[File::Constants@File-3A-3ASYNC-2C+File-3A-3ARSYNC-2C+and+File-3A-3ADSYNC]
{File
-
SHARE_DELETE =
:SHARE_DELETE}[File::Constants@File-3A-3ASHARE_DELETE]
{File
-
SYNC =
:SYNC}[File::Constants@File-3A-3ASYNC-2C+File-3A-3ARSYNC-2C+and+File-3A-3ADSYNC]
{File
-
TMPFILE =
:TMPFILE}[File::Constants@File-3A-3ATMPFILE]
{File
-
TRUNC =
:TRUNC}[File::Constants@File-3A-3ATRUNC]
{File
-
WRONLY =
:WRONLY}[File::Constants@File-3A-3AWRONLY]
{File