Class

A File object is a representation of a file in the underlying platform.

Class File extends module FileTest, supporting such singleton methods as File.exist?.

About the Examples

Many examples here use these variables:

# English text with newlines.
text = <<~EOT
  First line
  Second line

  Fourth line
  Fifth line
EOT

# Russian text.
russian = "\u{442 435 441 442}" # => "тест"

# Binary data.
data = "\u9990\u9991\u9992\u9993\u9994"

# Text file.
File.write('t.txt', text)

# File with Russian text.
File.write('t.rus', russian)

# File with binary data.
f = File.new('t.dat', 'wb:UTF-16')
f.write(data)
f.close

Access Modes

Methods File.new and File.open each create a File object for a given file path.

String Access Modes

Methods File.new and File.open each may take string argument mode, which:

Read/Write Mode

The read/write mode determines:

  • Whether the file is to be initially truncated.

  • Whether reading is allowed, and if so:

    • The initial read position in the file.

    • Where in the file reading can occur.

  • Whether writing is allowed, and if so:

    • The initial write position in the file.

    • Where in the file writing can occur.

These tables summarize:

Read/Write Modes for Existing File

|------|-----------|----------|----------|----------|-----------|
| R/W  | Initial   |          | Initial  |          | Initial   |
| Mode | Truncate? |  Read    | Read Pos |  Write   | Write Pos |
|------|-----------|----------|----------|----------|-----------|
| 'r'  |    No     | Anywhere |    0     |   Error  |     -     |
| 'w'  |    Yes    |   Error  |    -     | Anywhere |     0     |
| 'a'  |    No     |   Error  |    -     | End only |    End    |
| 'r+' |    No     | Anywhere |    0     | Anywhere |     0     |
| 'w+' |    Yes    | Anywhere |    0     | Anywhere |     0     |
| 'a+' |    No     | Anywhere |   End    | End only |    End    |
|------|-----------|----------|----------|----------|-----------|

Read/Write Modes for \File To Be Created

|------|----------|----------|----------|-----------|
| R/W  |          | Initial  |          | Initial   |
| Mode |  Read    | Read Pos |  Write   | Write Pos |
|------|----------|----------|----------|-----------|
| 'w'  |   Error  |    -     | Anywhere |     0     |
| 'a'  |   Error  |    -     | End only |     0     |
| 'w+' | Anywhere |    0     | Anywhere |     0     |
| 'a+' | Anywhere |    0     | End only |    End    |
|------|----------|----------|----------|-----------|

Note that modes 'r' and 'r+' are not allowed for a non-existent file (exception raised).

In the tables:

  • Anywhere means that methods IO#rewind, IO#pos=, and IO#seek may be used to change the file’s position, so that allowed reading or writing may occur anywhere in the file.

  • End only means that writing can occur only at end-of-file, and that methods IO#rewind, IO#pos=, and IO#seek do not affect writing.

  • Error means that an exception is raised if disallowed reading or writing is attempted.

Read/Write Modes for Existing File
  • 'r':

    • File is not initially truncated:

      f = File.new('t.txt') # => #<File:t.txt>
      f.size == 0           # => false
      
    • File’s initial read position is 0:

      f.pos # => 0
      
    • File may be read anywhere; see IO#rewind, IO#pos=, IO#seek:

      f.readline # => "First line\n"
      f.readline # => "Second line\n"
      
      f.rewind
      f.readline # => "First line\n"
      
      f.pos = 1
      f.readline # => "irst line\n"
      
      f.seek(1, :CUR)
      f.readline # => "econd line\n"
      
    • Writing is not allowed:

      f.write('foo') # Raises IOError.
      
  • 'w':

    • File is initially truncated:

      path = 't.tmp'
      File.write(path, text)
      f = File.new(path, 'w')
      f.size == 0 # => true
      
    • File’s initial write position is 0:

      f.pos # => 0
      
    • File may be written anywhere (even past end-of-file); see IO#rewind, IO#pos=, IO#seek:

      f.write('foo')
      f.flush
      File.read(path) # => "foo"
      f.pos # => 3
      
      f.write('bar')
      f.flush
      File.read(path) # => "foobar"
      f.pos # => 6
      
      f.rewind
      f.write('baz')
      f.flush
      File.read(path) # => "bazbar"
      f.pos # => 3
      
      f.pos = 3
      f.write('foo')
      f.flush
      File.read(path) # => "bazfoo"
      f.pos # => 6
      
      f.seek(-3, :END)
      f.write('bam')
      f.flush
      File.read(path) # => "bazbam"
      f.pos # => 6
      
      f.pos = 8
      f.write('bah')  # Zero padding as needed.
      f.flush
      File.read(path) # => "bazbam\u0000\u0000bah"
      f.pos # => 11
      
    • Reading is not allowed:

      f.read # Raises IOError.
      
  • 'a':

    • File is not initially truncated:

      path = 't.tmp'
      File.write(path, 'foo')
      f = File.new(path, 'a')
      f.size == 0 # => false
      
    • File’s initial position is 0 (but is ignored):

      f.pos # => 0
      
    • File may be written only at end-of-file; IO#rewind, IO#pos=, IO#seek do not affect writing:

      f.write('bar')
      f.flush
      File.read(path) # => "foobar"
      f.write('baz')
      f.flush
      File.read(path) # => "foobarbaz"
      
      f.rewind
      f.write('bat')
      f.flush
      File.read(path) # => "foobarbazbat"
      
    • Reading is not allowed:

      f.read # Raises IOError.
      
  • 'r+':

    • File is not initially truncated:

      path = 't.tmp'
      File.write(path, text)
      f = File.new(path, 'r+')
      f.size == 0 # => false
      
    • File’s initial read position is 0:

      f.pos # => 0
      
    • File may be read or written anywhere (even past end-of-file); see IO#rewind, IO#pos=, IO#seek:

      f.readline # => "First line\n"
      f.readline # => "Second line\n"
      
      f.rewind
      f.readline # => "First line\n"
      
      f.pos = 1
      f.readline # => "irst line\n"
      
      f.seek(1, :CUR)
      f.readline # => "econd line\n"
      
      f.rewind
      f.write('WWW')
      f.flush
      File.read(path)
      # => "WWWst line\nSecond line\nFourth line\nFifth line\n"
      
      f.pos = 10
      f.write('XXX')
      f.flush
      File.read(path)
      # => "WWWst lineXXXecond line\nFourth line\nFifth line\n"
      
      f.seek(-6, :END)
      # => 0
      f.write('YYY')
      # => 3
      f.flush
      # => #<File:t.tmp>
      File.read(path)
      # => "WWWst lineXXXecond line\nFourth line\nFifth YYYe\n"
      
      f.seek(2, :END)
      f.write('ZZZ') # Zero padding as needed.
      f.flush
      File.read(path)
      # => "WWWst lineXXXecond line\nFourth line\nFifth YYYe\n\u0000\u0000ZZZ"
      
  • 'a+':

    • File is not initially truncated:

      path = 't.tmp'
      File.write(path, 'foo')
      f = File.new(path, 'a+')
      f.size == 0 # => false
      
    • File’s initial read position is 0:

      f.pos # => 0
      
    • File may be written only at end-of-file; IO#rewind, IO#pos=, IO#seek do not affect writing:

      f.write('bar')
      f.flush
      File.read(path)      # => "foobar"
      f.write('baz')
      f.flush
      File.read(path)      # => "foobarbaz"
      
      f.rewind
      f.write('bat')
      f.flush
      File.read(path) # => "foobarbazbat"
      
    • File may be read anywhere; see IO#rewind, IO#pos=, IO#seek:

      f.rewind
      f.read # => "foobarbazbat"
      
      f.pos = 3
      f.read # => "barbazbat"
      
      f.seek(-3, :END)
      f.read # => "bat"
      
Read/Write Modes for File To Be Created

Note that modes 'r' and 'r+' are not allowed for a non-existent file (exception raised).

  • 'w':

    • File’s initial write position is 0:

      path = 't.tmp'
      FileUtils.rm_f(path)
      f = File.new(path, 'w')
      f.pos # => 0
      
    • File may be written anywhere (even past end-of-file); see IO#rewind, IO#pos=, IO#seek:

      f.write('foo')
      f.flush
      File.read(path) # => "foo"
      f.pos # => 3
      
      f.write('bar')
      f.flush
      File.read(path) # => "foobar"
      f.pos # => 6
      
      f.rewind
      f.write('baz')
      f.flush
      File.read(path) # => "bazbar"
      f.pos # => 3
      
      f.pos = 3
      f.write('foo')
      f.flush
      File.read(path) # => "bazfoo"
      f.pos # => 6
      
      f.seek(-3, :END)
      f.write('bam')
      f.flush
      File.read(path) # => "bazbam"
      f.pos # => 6
      
      f.pos = 8
      f.write('bah')  # Zero padding as needed.
      f.flush
      File.read(path) # => "bazbam\u0000\u0000bah"
      f.pos # => 11
      
    • Reading is not allowed:

      f.read # Raises IOError.
      
  • 'a':

    • File’s initial write position is 0:

      path = 't.tmp'
      FileUtils.rm_f(path)
      f = File.new(path, 'a')
      f.pos # => 0
      
    • Writing occurs only at end-of-file:

      f.write('foo')
      f.pos # => 3
      f.write('bar')
      f.pos # => 6
      f.flush
      File.read(path) # => "foobar"
      
      f.rewind
      f.write('baz')
      f.flush
      File.read(path) # => "foobarbaz"
      
    • Reading is not allowed:

      f.read # Raises IOError.
      
  • 'w+':

    • File’s initial position is 0:

      path = 't.tmp'
      FileUtils.rm_f(path)
      f = File.new(path, 'w+')
      f.pos # => 0
      
    • File may be written anywhere (even past end-of-file); see IO#rewind, IO#pos=, IO#seek:

      f.write('foo')
      f.flush
      File.read(path) # => "foo"
      f.pos # => 3
      
      f.write('bar')
      f.flush
      File.read(path) # => "foobar"
      f.pos # => 6
      
      f.rewind
      f.write('baz')
      f.flush
      File.read(path) # => "bazbar"
      f.pos # => 3
      
      f.pos = 3
      f.write('foo')
      f.flush
      File.read(path) # => "bazfoo"
      f.pos # => 6
      
      f.seek(-3, :END)
      f.write('bam')
      f.flush
      File.read(path) # => "bazbam"
      f.pos # => 6
      
      f.pos = 8
      f.write('bah')  # Zero padding as needed.
      f.flush
      File.read(path) # => "bazbam\u0000\u0000bah"
      f.pos # => 11
      
    • File may be read anywhere (even past end-of-file); see IO#rewind, IO#pos=, IO#seek:

      f.rewind
      # => 0
      f.read
      # => "bazbam\u0000\u0000bah"
      
      f.pos = 3
      # => 3
      f.read
      # => "bam\u0000\u0000bah"
      
      f.seek(-3, :END)
      # => 0
      f.read
      # => "bah"
      
  • 'a+':

    • File’s initial write position is 0:

      path = 't.tmp'
      FileUtils.rm_f(path)
      f = File.new(path, 'a+')
      f.pos # => 0
      
    • Writing occurs only at end-of-file:

      f.write('foo')
      f.pos # => 3
      f.write('bar')
      f.pos # => 6
      f.flush
      File.read(path) # => "foobar"
      
      f.rewind
      f.write('baz')
      f.flush
      File.read(path) # => "foobarbaz"
      
    • File may be read anywhere (even past end-of-file); see IO#rewind, IO#pos=, IO#seek:

      f.rewind
      f.read # => "foobarbaz"
      
      f.pos = 3
      f.read # => "barbaz"
      
      f.seek(-3, :END)
      f.read # => "baz"
      
      f.pos = 800
      f.read # => ""
      

Data Mode

To specify whether data is to be treated as text or as binary data, either of the following may be suffixed to any of the string read/write modes above:

  • 't': Text data; sets the default external encoding to Encoding::UTF_8; on Windows, enables conversion between EOL and CRLF and enables interpreting 0x1A as an end-of-file marker.

  • 'b': Binary data; sets the default external encoding to Encoding::ASCII_8BIT; on Windows, suppresses conversion between EOL and CRLF and disables interpreting 0x1A as an end-of-file marker.

If neither is given, the stream defaults to text data.

Examples:

File.new('t.txt', 'rt')
File.new('t.dat', 'rb')

When the data mode is specified, the read/write mode may not be omitted, and the data mode must precede the file-create mode, if given:

File.new('t.dat', 'b')   # Raises an exception.
File.new('t.dat', 'rxb') # Raises an exception.

File-Create Mode

The following may be suffixed to any writable string mode above:

  • 'x': Creates the file if it does not exist; raises an exception if the file exists.

Example:

File.new('t.tmp', 'wx')

When the file-create mode is specified, the read/write mode may not be omitted, and the file-create mode must follow the data mode:

File.new('t.dat', 'x')   # Raises an exception.
File.new('t.dat', 'rxb') # Raises an exception.

Integer Access Modes

When mode is an integer it must be one or more of the following constants, which may be combined by the bitwise OR operator |:

  • File::RDONLY: Open for reading only.

  • File::WRONLY: Open for writing only.

  • File::RDWR: Open for reading and writing.

  • File::APPEND: Open for appending only.

Examples:

File.new('t.txt', File::RDONLY)
File.new('t.tmp', File::RDWR | File::CREAT | File::EXCL)

Note: Method IO#set_encoding does not allow the mode to be specified as an integer.

File-Create Mode Specified as an Integer

These constants may also be ORed into the integer mode:

  • File::CREAT: Create file if it does not exist.

  • File::EXCL: Raise an exception if File::CREAT is given and the file exists.

Data Mode Specified as an Integer

Data mode cannot be specified as an integer. When the stream access mode is given as an integer, the data mode is always text, never binary.

Note that although there is a constant File::BINARY, setting its value in an integer stream mode has no effect; this is because, as documented in File::Constants, the File::BINARY value disables line code conversion, but does not change the external encoding.

Encodings

Any of the string modes above may specify encodings - either external encoding only or both external and internal encodings - by appending one or both encoding names, separated by colons:

f = File.new('t.dat', 'rb')
f.external_encoding # => #<Encoding:ASCII-8BIT>
f.internal_encoding # => nil
f = File.new('t.dat', 'rb:UTF-16')
f.external_encoding # => #<Encoding:UTF-16 (dummy)>
f.internal_encoding # => nil
f = File.new('t.dat', 'rb:UTF-16:UTF-16')
f.external_encoding # => #<Encoding:UTF-16 (dummy)>
f.internal_encoding # => #<Encoding:UTF-16>
f.close

The numerous encoding names are available in array Encoding.name_list:

Encoding.name_list.take(3) # => ["ASCII-8BIT", "UTF-8", "US-ASCII"]

When the external encoding is set, strings read are tagged by that encoding when reading, and strings written are converted to that encoding when writing.

When both external and internal encodings are set, strings read are converted from external to internal encoding, and strings written are converted from internal to external encoding. For further details about transcoding input and output, see Encodings.

If the external encoding is 'BOM|UTF-8', 'BOM|UTF-16LE' or 'BOM|UTF16-BE', Ruby checks for a Unicode BOM in the input document to help determine the encoding. For UTF-16 encodings the file open mode must be binary. If the BOM is found, it is stripped and the external encoding from the BOM is used.

Note that the BOM-style encoding option is case insensitive, so 'bom|utf-8' is also valid.

File Permissions

A File object has permissions, an octal integer representing the permissions of an actual file in the underlying platform.

Note that file permissions are quite different from the mode of a file stream (File object).

In a File object, the permissions are available thus, where method mode, despite its name, returns permissions:

f = File.new('t.txt')
f.lstat.mode.to_s(8) # => "100644"

On a Unix-based operating system, the three low-order octal digits represent the permissions for owner (6), group (4), and world (4). The triplet of bits in each octal digit represent, respectively, read, write, and execute permissions.

Permissions 0644 thus represent read-write access for owner and read-only access for group and world. See man pages open(2) and chmod(2).

For a directory, the meaning of the execute bit changes: when set, the directory can be searched.

Higher-order bits in permissions may indicate the type of file (plain, directory, pipe, socket, etc.) and various other special features.

On non-Posix operating systems, permissions may include only read-only or read-write, in which case, the remaining permission will resemble typical values. On Windows, for instance, the default permissions are 0644; The only change that can be made is to make the file read-only, which is reported as 0444.

For a method that actually creates a file in the underlying platform (as opposed to merely creating a File object), permissions may be specified:

File.new('t.tmp', File::CREAT, 0644)
File.new('t.tmp', File::CREAT, 0444)

Permissions may also be changed:

f = File.new('t.tmp', File::CREAT, 0444)
f.chmod(0644)
f.chmod(0444)

File Constants

Various constants for use in File and IO methods may be found in module File::Constants; an array of their names is returned by File::Constants.constants.

What’s Here

First, what’s elsewhere. Class File:

  • Inherits from class IO, in particular, methods for creating, reading, and writing files

  • Includes module FileTest, which provides dozens of additional methods.

Here, class File provides methods that are useful for:

Creating

  • ::new: Opens the file at the given path; returns the file.

  • ::open: Same as ::new, but when given a block will yield the file to the block, and close the file upon exiting the block.

  • ::link: Creates a new name for an existing file using a hard link.

  • ::mkfifo: Returns the FIFO file created at the given path.

  • ::symlink: Creates a symbolic link for the given file path.

Querying

Paths

  • ::absolute_path: Returns the absolute file path for the given path.

  • ::absolute_path?: Returns whether the given path is the absolute file path.

  • ::basename: Returns the last component of the given file path.

  • ::dirname: Returns all but the last component of the given file path.

  • ::expand_path: Returns the absolute file path for the given path, expanding ~ for a home directory.

  • ::extname: Returns the file extension for the given file path.

  • ::fnmatch? (aliased as ::fnmatch): Returns whether the given file path matches the given pattern.

  • ::join: Joins path components into a single path string.

  • ::path: Returns the string representation of the given path.

  • ::readlink: Returns the path to the file at the given symbolic link.

  • ::realdirpath: Returns the real path for the given file path, where the last component need not exist.

  • ::realpath: Returns the real path for the given file path, where all components must exist.

  • ::split: Returns an array of two strings: the directory name and basename of the file at the given path.

  • path (aliased as to_path): Returns the string representation of the given path.

Times

  • ::atime: Returns a Time for the most recent access to the given file.

  • ::birthtime: Returns a Time for the creation of the given file.

  • ::ctime: Returns a Time for the metadata change of the given file.

  • ::mtime: Returns a Time for the most recent data modification to the content of the given file.

  • atime: Returns a Time for the most recent access to self.

  • birthtime: Returns a Time the creation for self.

  • ctime: Returns a Time for the metadata change of self.

  • mtime: Returns a Time for the most recent data modification to the content of self.

Types

  • ::blockdev?: Returns whether the file at the given path is a block device.

  • ::chardev?: Returns whether the file at the given path is a character device.

  • ::directory?: Returns whether the file at the given path is a directory.

  • ::executable?: Returns whether the file at the given path is executable by the effective user and group of the current process.

  • ::executable_real?: Returns whether the file at the given path is executable by the real user and group of the current process.

  • ::exist?: Returns whether the file at the given path exists.

  • ::file?: Returns whether the file at the given path is a regular file.

  • ::ftype: Returns a string giving the type of the file at the given path.

  • ::grpowned?: Returns whether the effective group of the current process owns the file at the given path.

  • ::identical?: Returns whether the files at two given paths are identical.

  • ::lstat: Returns the File::Stat object for the last symbolic link in the given path.

  • ::owned?: Returns whether the effective user of the current process owns the file at the given path.

  • ::pipe?: Returns whether the file at the given path is a pipe.

  • ::readable?: Returns whether the file at the given path is readable by the effective user and group of the current process.

  • ::readable_real?: Returns whether the file at the given path is readable by the real user and group of the current process.

  • ::setgid?: Returns whether the setgid bit is set for the file at the given path.

  • ::setuid?: Returns whether the setuid bit is set for the file at the given path.

  • ::socket?: Returns whether the file at the given path is a socket.

  • ::stat: Returns the File::Stat object for the file at the given path.

  • ::sticky?: Returns whether the file at the given path has its sticky bit set.

  • ::symlink?: Returns whether the file at the given path is a symbolic link.

  • ::umask: Returns the umask value for the current process.

  • ::world_readable?: Returns whether the file at the given path is readable by others.

  • ::world_writable?: Returns whether the file at the given path is writable by others.

  • ::writable?: Returns whether the file at the given path is writable by the effective user and group of the current process.

  • ::writable_real?: Returns whether the file at the given path is writable by the real user and group of the current process.

  • lstat: Returns the File::Stat object for the last symbolic link in the path for self.

Contents

  • ::empty? (aliased as ::zero?): Returns whether the file at the given path exists and is empty.

  • ::size: Returns the size (bytes) of the file at the given path.

  • ::size?: Returns nil if there is no file at the given path, or if that file is empty; otherwise returns the file size (bytes).

  • size: Returns the size (bytes) of self.

Settings

  • ::chmod: Changes permissions of the file at the given path.

  • ::chown: Change ownership of the file at the given path.

  • ::lchmod: Changes permissions of the last symbolic link in the given path.

  • ::lchown: Change ownership of the last symbolic in the given path.

  • ::lutime: For each given file path, sets the access time and modification time of the last symbolic link in the path.

  • ::rename: Moves the file at one given path to another given path.

  • ::utime: Sets the access time and modification time of each file at the given paths.

  • flock: Locks or unlocks self.

Other

  • ::truncate: Truncates the file at the given file path to the given size.

  • ::unlink (aliased as ::delete): Deletes the file for each given file path.

  • truncate: Truncates self to the given size.

Constants

separates directory parts in path

separates directory parts in path

platform specific alternative separator

path list separator

Class Methods

Converts a pathname to an absolute pathname. Relative paths are referenced from the current working directory of the process unless dir_string is given, in which case it will be used as the starting point. If the given pathname starts with a “~” it is NOT expanded, it is treated as a normal directory name.

File.absolute_path("~oracle/bin")       #=> "<relative_path>/~oracle/bin"

Returns true if file_name is an absolute path, and false otherwise.

File.absolute_path?("c:/foo")     #=> false (on Linux), true (on Windows)

Returns the last access time for the named file as a Time object.

file_name can be an IO object.

File.atime("testfile")   #=> Wed Apr 09 08:51:48 CDT 2003

Returns the last component of the filename given in file_name (after first stripping trailing separators), which can be formed using both File::SEPARATOR and File::ALT_SEPARATOR as the separator when File::ALT_SEPARATOR is not nil. If suffix is given and present at the end of file_name, it is removed. If suffix is “.*”, any extension will be removed.

File.basename("/home/gumby/work/ruby.rb")          #=> "ruby.rb"
File.basename("/home/gumby/work/ruby.rb", ".rb")   #=> "ruby"
File.basename("/home/gumby/work/ruby.rb", ".*")    #=> "ruby"

Returns the birth time for the named file.

file_name can be an IO object.

File.birthtime("testfile")   #=> Wed Apr 09 08:53:13 CDT 2003

If the platform doesn’t have birthtime, raises NotImplementedError.

Returns true if filepath points to a block device, false otherwise:

File.blockdev?('/dev/sda1')       # => true
File.blockdev?(File.new('t.tmp')) # => false

Returns true if filepath points to a character device, false otherwise.

File.chardev?($stdin)     # => true
File.chardev?('t.txt')     # => false

Changes permission bits on the named file(s) to the bit pattern represented by mode_int. Actual effects are operating system dependent (see the beginning of this section). On Unix systems, see chmod(2) for details. Returns the number of files processed.

File.chmod(0644, "testfile", "out")   #=> 2

Changes the owner and group of the named file(s) to the given numeric owner and group id’s. Only a process with superuser privileges may change the owner of a file. The current owner of a file may change the file’s group to any group to which the owner belongs. A nil or -1 owner or group id is ignored. Returns the number of files processed.

File.chown(nil, 100, "testfile")

Returns the change time for the named file (the time at which directory information about the file was changed, not the file itself).

file_name can be an IO object.

Note that on Windows (NTFS), returns creation time (birth time).

File.ctime("testfile")   #=> Wed Apr 09 08:53:13 CDT 2003

Deletes the named files, returning the number of names passed as arguments. Raises an exception on any error. Since the underlying implementation relies on the unlink(2) system call, the type of exception raised depends on its error type (see linux.die.net/man/2/unlink) and has the form of e.g. Errno::ENOENT.

See also Dir::rmdir.

With string object given, returns true if path is a string path leading to a directory, or to a symbolic link to a directory; false otherwise:

File.directory?('.')              # => true
File.directory?('foo')            # => false
File.symlink('.', 'dirlink')      # => 0
File.directory?('dirlink')        # => true
File.symlink('t,txt', 'filelink') # => 0
File.directory?('filelink')       # => false

Argument path can be an IO object.

Returns all components of the filename given in file_name except the last one (after first stripping trailing separators). The filename can be formed using both File::SEPARATOR and File::ALT_SEPARATOR as the separator when File::ALT_SEPARATOR is not nil.

File.dirname("/home/gumby/work/ruby.rb")   #=> "/home/gumby/work"

If level is given, removes the last level components, not only one.

File.dirname("/home/gumby/work/ruby.rb", 2) #=> "/home/gumby"
File.dirname("/home/gumby/work/ruby.rb", 4) #=> "/"

Returns true if the named file exists and has a zero size.

file_name can be an IO object.

Returns true if the named file is executable by the effective user and group id of this process. See eaccess(3).

Windows does not support execute permissions separately from read permissions. On Windows, a file is only considered executable if it ends in .bat, .cmd, .com, or .exe.

Note that some OS-level security features may cause this to return true even though the file is not executable by the effective user/group.

Returns true if the named file is executable by the real user and group id of this process. See access(3).

Windows does not support execute permissions separately from read permissions. On Windows, a file is only considered executable if it ends in .bat, .cmd, .com, or .exe.

Note that some OS-level security features may cause this to return true even though the file is not executable by the real user/group.

Return true if the named file exists.

file_name can be an IO object.

“file exists” means that stat() or fstat() system call is successful.

Converts a pathname to an absolute pathname. Relative paths are referenced from the current working directory of the process unless dir_string is given, in which case it will be used as the starting point. The given pathname may start with a “~”, which expands to the process owner’s home directory (the environment variable HOME must be set correctly). “~user” expands to the named user’s home directory.

File.expand_path("~oracle/bin")           #=> "/home/oracle/bin"

A simple example of using dir_string is as follows.

File.expand_path("ruby", "/usr/bin")      #=> "/usr/bin/ruby"

A more complex example which also resolves parent directory is as follows. Suppose we are in bin/mygem and want the absolute path of lib/mygem.rb.

File.expand_path("../../lib/mygem.rb", __FILE__)
#=> ".../path/to/project/lib/mygem.rb"

So first it resolves the parent of __FILE__, that is bin/, then go to the parent, the root of the project and appends lib/mygem.rb.

Returns the extension (the portion of file name in path starting from the last period).

If path is a dotfile, or starts with a period, then the starting dot is not dealt with the start of the extension.

An empty string will also be returned when the period is the last character in path.

On Windows, trailing dots are truncated.

File.extname("test.rb")         #=> ".rb"
File.extname("a/b/d/test.rb")   #=> ".rb"
File.extname(".a/b/d/test.rb")  #=> ".rb"
File.extname("foo.")            #=> "" on Windows
File.extname("foo.")            #=> "." on non-Windows
File.extname("test")            #=> ""
File.extname(".profile")        #=> ""
File.extname(".profile.sh")     #=> ".sh"

Returns true if the named file exists and is a regular file.

file can be an IO object.

If the file argument is a symbolic link, it will resolve the symbolic link and use the file referenced by the link.

Returns true if path matches against pattern. The pattern is not a regular expression; instead it follows rules similar to shell filename globbing. It may contain the following metacharacters:

*

Matches any file. Can be restricted by other values in the glob. Equivalent to /.*/x in regexp.

*

Matches all regular files

c*

Matches all files beginning with c

*c

Matches all files ending with c

*c*

Matches all files that have c in them (including at the beginning or end).

To match hidden files (that start with a .) set the File::FNM_DOTMATCH flag.

**

Matches directories recursively or files expansively.

?

Matches any one character. Equivalent to /.{1}/ in regexp.

[set]

Matches any one character in set. Behaves exactly like character sets in Regexp, including set negation ([^a-z]).

\

Escapes the next metacharacter.

{a,b}

Matches pattern a and pattern b if File::FNM_EXTGLOB flag is enabled. Behaves like a Regexp union ((?:a|b)).

flags is a bitwise OR of the FNM_XXX constants. The same glob pattern and flags are used by Dir::glob.

Examples:

File.fnmatch('cat',       'cat')        #=> true  # match entire string
File.fnmatch('cat',       'category')   #=> false # only match partial string

File.fnmatch('c{at,ub}s', 'cats')                    #=> false # { } isn't supported by default
File.fnmatch('c{at,ub}s', 'cats', File::FNM_EXTGLOB) #=> true  # { } is supported on FNM_EXTGLOB

File.fnmatch('c?t',     'cat')          #=> true  # '?' match only 1 character
File.fnmatch('c??t',    'cat')          #=> false # ditto
File.fnmatch('c*',      'cats')         #=> true  # '*' match 0 or more characters
File.fnmatch('c*t',     'c/a/b/t')      #=> true  # ditto
File.fnmatch('ca[a-z]', 'cat')          #=> true  # inclusive bracket expression
File.fnmatch('ca[^t]',  'cat')          #=> false # exclusive bracket expression ('^' or '!')

File.fnmatch('cat', 'CAT')                     #=> false # case sensitive
File.fnmatch('cat', 'CAT', File::FNM_CASEFOLD) #=> true  # case insensitive
File.fnmatch('cat', 'CAT', File::FNM_SYSCASE)  #=> true or false # depends on the system default

File.fnmatch('?',   '/', File::FNM_PATHNAME)  #=> false # wildcard doesn't match '/' on FNM_PATHNAME
File.fnmatch('*',   '/', File::FNM_PATHNAME)  #=> false # ditto
File.fnmatch('[/]', '/', File::FNM_PATHNAME)  #=> false # ditto

File.fnmatch('\?',   '?')                       #=> true  # escaped wildcard becomes ordinary
File.fnmatch('\a',   'a')                       #=> true  # escaped ordinary remains ordinary
File.fnmatch('\a',   '\a', File::FNM_NOESCAPE)  #=> true  # FNM_NOESCAPE makes '\' ordinary
File.fnmatch('[\?]', '?')                       #=> true  # can escape inside bracket expression

File.fnmatch('*',   '.profile')                      #=> false # wildcard doesn't match leading
File.fnmatch('*',   '.profile', File::FNM_DOTMATCH)  #=> true  # period by default.
File.fnmatch('.*',  '.profile')                      #=> true

File.fnmatch('**/*.rb', 'main.rb')                  #=> false
File.fnmatch('**/*.rb', './main.rb')                #=> false
File.fnmatch('**/*.rb', 'lib/song.rb')              #=> true
File.fnmatch('**.rb', 'main.rb')                    #=> true
File.fnmatch('**.rb', './main.rb')                  #=> false
File.fnmatch('**.rb', 'lib/song.rb')                #=> true
File.fnmatch('*',     'dave/.profile')              #=> true

File.fnmatch('**/foo', 'a/b/c/foo', File::FNM_PATHNAME)     #=> true
File.fnmatch('**/foo', '/a/b/c/foo', File::FNM_PATHNAME)    #=> true
File.fnmatch('**/foo', 'c:/a/b/c/foo', File::FNM_PATHNAME)  #=> true
File.fnmatch('**/foo', 'a/.b/c/foo', File::FNM_PATHNAME)    #=> false
File.fnmatch('**/foo', 'a/.b/c/foo', File::FNM_PATHNAME | File::FNM_DOTMATCH) #=> true

Identifies the type of the named file; the return string is one of “file”, “directory”, “characterSpecial”, “blockSpecial”, “fifo”, “link”, “socket”, or “unknown”.

File.ftype("testfile")            #=> "file"
File.ftype("/dev/tty")            #=> "characterSpecial"
File.ftype("/tmp/.X11-unix/X0")   #=> "socket"

Returns true if the named file exists and the effective group id of the calling process is the owner of the file. Returns false on Windows.

file_name can be an IO object.

Returns true if the named files are identical.

file_1 and file_2 can be an IO object.

open("a", "w") {}
p File.identical?("a", "a")      #=> true
p File.identical?("a", "./a")    #=> true
File.link("a", "b")
p File.identical?("a", "b")      #=> true
File.symlink("a", "c")
p File.identical?("a", "c")      #=> true
open("d", "w") {}
p File.identical?("a", "d")      #=> false

Returns a new string formed by joining the strings using "/".

File.join("usr", "mail", "gumby")   #=> "usr/mail/gumby"

Equivalent to File::chmod, but does not follow symbolic links (so it will change the permissions associated with the link, not the file referenced by the link). Often not available.

Equivalent to File::chown, but does not follow symbolic links (so it will change the owner associated with the link, not the file referenced by the link). Often not available. Returns number of files in the argument list.

Creates a new name for an existing file using a hard link. Will not overwrite new_name if it already exists (raising a subclass of SystemCallError). Not available on all platforms.

File.link("testfile", ".testfile")   #=> 0
IO.readlines(".testfile")[0]         #=> "This is line one\n"

Like File::stat, but does not follow the last symbolic link; instead, returns a File::Stat object for the link itself.

File.symlink('t.txt', 'symlink')
File.stat('symlink').size  # => 47
File.lstat('symlink').size # => 5

Sets the access and modification times of each named file to the first two arguments. If a file is a symlink, this method acts upon the link itself as opposed to its referent; for the inverse behavior, see File.utime. Returns the number of file names in the argument list.

Creates a FIFO special file with name file_name. mode specifies the FIFO’s permissions. It is modified by the process’s umask in the usual way: the permissions of the created file are (mode & ~umask).

Returns the modification time for the named file as a Time object.

file_name can be an IO object.

File.mtime("testfile")   #=> Tue Apr 08 12:58:04 CDT 2003

Opens the file at the given path according to the given mode; creates and returns a new File object for that file.

The new File object is buffered mode (or non-sync mode), unless filename is a tty. See IO#flush, IO#fsync, IO#fdatasync, and IO#sync=.

Argument path must be a valid file path:

f = File.new('/etc/fstab')
f.close
f = File.new('t.txt')
f.close

Optional argument mode (defaults to ‘r’) must specify a valid mode; see Access Modes:

f = File.new('t.tmp', 'w')
f.close
f = File.new('t.tmp', File::RDONLY)
f.close

Optional argument perm (defaults to 0666) must specify valid permissions see File Permissions:

f = File.new('t.tmp', File::CREAT, 0644)
f.close
f = File.new('t.tmp', File::CREAT, 0444)
f.close

Optional keyword arguments opts specify:

Creates a new File object, via File.new with the given arguments.

With no block given, returns the File object.

With a block given, calls the block with the File object and returns the block’s value.

Returns true if the named file exists and the effective used id of the calling process is the owner of the file.

file_name can be an IO object.

Returns the string representation of the path

File.path(File::NULL)           #=> "/dev/null"
File.path(Pathname.new("/tmp")) #=> "/tmp"

Returns true if filepath points to a pipe, false otherwise:

File.mkfifo('tmp/fifo')
File.pipe?('tmp/fifo') # => true
File.pipe?('t.txt')    # => false

Returns true if the named file is readable by the effective user and group id of this process. See eaccess(3).

Note that some OS-level security features may cause this to return true even though the file is not readable by the effective user/group.

Returns true if the named file is readable by the real user and group id of this process. See access(3).

Note that some OS-level security features may cause this to return true even though the file is not readable by the real user/group.

Returns the name of the file referenced by the given link. Not available on all platforms.

File.symlink("testfile", "link2test")   #=> 0
File.readlink("link2test")              #=> "testfile"

Returns the real (absolute) pathname of pathname in the actual filesystem. The real pathname doesn’t contain symlinks or useless dots.

If dir_string is given, it is used as a base directory for interpreting relative pathname instead of the current directory.

The last component of the real pathname can be nonexistent.

Returns the real (absolute) pathname of pathname in the actual filesystem not containing symlinks or useless dots.

If dir_string is given, it is used as a base directory for interpreting relative pathname instead of the current directory.

All components of the pathname must exist when this method is called.

Renames the given file to the new name. Raises a SystemCallError if the file cannot be renamed.

File.rename("afile", "afile.bak")   #=> 0

Returns true if the named file has the setgid bit set.

file_name can be an IO object.

Returns true if the named file has the setuid bit set.

file_name can be an IO object.

Returns the size of file_name.

file_name can be an IO object.

Returns nil if file_name doesn’t exist or has zero size, the size of the file otherwise.

file_name can be an IO object.

Returns true if filepath points to a socket, false otherwise:

require 'socket'
File.socket?(Socket.new(:INET, :STREAM)) # => true
File.socket?(File.new('t.txt'))          # => false

Splits the given string into a directory and a file component and returns them in a two-element array. See also File::dirname and File::basename.

File.split("/home/gumby/.profile")   #=> ["/home/gumby", ".profile"]

Returns a File::Stat object for the file at filepath (see File::Stat):

File.stat('t.txt').class # => File::Stat

Returns true if the named file has the sticky bit set.

file_name can be an IO object.

Creates a symbolic link called new_name for the existing file old_name. Raises a NotImplemented exception on platforms that do not support symbolic links.

File.symlink("testfile", "link2test")   #=> 0

Returns true if filepath points to a symbolic link, false otherwise:

symlink = File.symlink('t.txt', 'symlink')
File.symlink?('symlink') # => true
File.symlink?('t.txt')   # => false

Truncates the file file_name to be at most integer bytes long. Not available on all platforms.

f = File.new("out", "w")
f.write("1234567890")     #=> 10
f.close                   #=> nil
File.truncate("out", 5)   #=> 0
File.size("out")          #=> 5

Returns the current umask value for this process. If the optional argument is given, set the umask to that value and return the previous value. Umask values are subtracted from the default permissions, so a umask of 0222 would make a file read-only for everyone.

File.umask(0006)   #=> 18
File.umask         #=> 6

Deletes the named files, returning the number of names passed as arguments. Raises an exception on any error. Since the underlying implementation relies on the unlink(2) system call, the type of exception raised depends on its error type (see linux.die.net/man/2/unlink) and has the form of e.g. Errno::ENOENT.

See also Dir::rmdir.

Sets the access and modification times of each named file to the first two arguments. If a file is a symlink, this method acts upon its referent rather than the link itself; for the inverse behavior see File.lutime. Returns the number of file names in the argument list.

If file_name is readable by others, returns an integer representing the file permission bits of file_name. Returns nil otherwise. The meaning of the bits is platform dependent; on Unix systems, see stat(2).

file_name can be an IO object.

File.world_readable?("/etc/passwd")           #=> 420
m = File.world_readable?("/etc/passwd")
sprintf("%o", m)                              #=> "644"

If file_name is writable by others, returns an integer representing the file permission bits of file_name. Returns nil otherwise. The meaning of the bits is platform dependent; on Unix systems, see stat(2).

file_name can be an IO object.

File.world_writable?("/tmp")                  #=> 511
m = File.world_writable?("/tmp")
sprintf("%o", m)                              #=> "777"

Returns true if the named file is writable by the effective user and group id of this process. See eaccess(3).

Note that some OS-level security features may cause this to return true even though the file is not writable by the effective user/group.

Returns true if the named file is writable by the real user and group id of this process. See access(3).

Note that some OS-level security features may cause this to return true even though the file is not writable by the real user/group.

Returns true if the named file exists and has a zero size.

file_name can be an IO object.

Instance Methods

Returns the last access time (a Time object) for file, or epoch if file has not been accessed.

File.new("testfile").atime   #=> Wed Dec 31 18:00:00 CST 1969

Returns the birth time for file.

File.new("testfile").birthtime   #=> Wed Apr 09 08:53:14 CDT 2003

If the platform doesn’t have birthtime, raises NotImplementedError.

Changes permission bits on file to the bit pattern represented by mode_int. Actual effects are platform dependent; on Unix systems, see chmod(2) for details. Follows symbolic links. Also see File#lchmod.

f = File.new("out", "w");
f.chmod(0644)   #=> 0

Changes the owner and group of file to the given numeric owner and group id’s. Only a process with superuser privileges may change the owner of a file. The current owner of a file may change the file’s group to any group to which the owner belongs. A nil or -1 owner or group id is ignored. Follows symbolic links. See also File#lchown.

File.new("testfile").chown(502, 1000)

Returns the change time for file (that is, the time directory information about the file was changed, not the file itself).

Note that on Windows (NTFS), returns creation time (birth time).

File.new("testfile").ctime   #=> Wed Apr 09 08:53:14 CDT 2003

Locks or unlocks file self according to the given locking_constant, a bitwise OR of the values in the table below.

Not available on all platforms.

Returns false if File::LOCK_NB is specified and the operation would have blocked; otherwise returns 0.



Constant Lock Effect
File::LOCK_EX Exclusive Only one process may hold an exclusive lock for self at a time.
File::LOCK_NB Non-blocking No blocking; may be combined with File::LOCK_SH or File::LOCK_EX using the bitwise OR operator |.
File::LOCK_SH Shared Multiple processes may each hold a shared lock for self at the same time.
File::LOCK_UN Unlock Remove an existing lock held by this process.



Example:

# Update a counter using an exclusive lock.
# Don't use File::WRONLY because it truncates the file.
File.open('counter', File::RDWR | File::CREAT, 0644) do |f|
  f.flock(File::LOCK_EX)
  value = f.read.to_i + 1
  f.rewind
  f.write("#{value}\n")
  f.flush
  f.truncate(f.pos)
end

# Read the counter using a shared lock.
File.open('counter', 'r') do |f|
  f.flock(File::LOCK_SH)
  f.read
end

Like File#stat, but does not follow the last symbolic link; instead, returns a File::Stat object for the link itself:

File.symlink('t.txt', 'symlink')
f = File.new('symlink')
f.stat.size  # => 47
f.lstat.size # => 11

Returns the modification time for file.

File.new("testfile").mtime   #=> Wed Apr 09 08:53:14 CDT 2003

Returns the size of file in bytes.

File.new("testfile").size   #=> 66

Truncates file to at most integer bytes. The file must be opened for writing. Not available on all platforms.

f = File.new("out", "w")
f.syswrite("1234567890")   #=> 10
f.truncate(5)              #=> 0
f.close()                  #=> nil
File.size("out")           #=> 5