class File

Opens the file named by filename.

mode must be one of the following file open modes:

Mode | Description
-----+------------------------------------------------------
r    | Read-only, starts at the beginning of the file.
r+   | Read-write, starts at the beginning of the file.
w    | Write-only, truncates existing file to zero length or
     | creates a new file if the file doesn't exist.
w+   | Read-write, truncates existing file to zero length or
     | creates a new file if the file doesn't exist.
a    | Write-only, starts at the end of the file,
     | creates a new file if the file doesn't exist.
a+   | Read-write, starts at the end of the file,
     | creates a new file if the file doesn't exist.
rb   | Same as 'r' but in binary file mode.
wb   | Same as 'w' but in binary file mode.
ab   | Same as 'a' but in binary file mode.

In binary file mode, line endings are not converted to CRLF on Windows.

Opens the file named by filename. If a file is being created, its initial permissions may be set using the perm parameter.

See self.new for what mode can be.

Returns the last component of the given path.

If suffix is present at the end of path, it is removed.

File.basename("/foo/bar/file.cr", ".cr") # => "file"

Returns the last component of the given path.

File.basename("/foo/bar/file.cr") # => "file.cr"

Changes the permissions of the specified file.

Symlinks are dereferenced, so that only the permissions of the symlink destination are changed, never the permissions of the symlink itself.

File.chmod("foo", 0o755)
File.info("foo").permissions.value # => 0o755

File.chmod("foo", 0o700)
File.info("foo").permissions.value # => 0o700

Changes the owner of the specified file.

File.chown("/foo/bar/baz.cr", 1001, 100)
File.chown("/foo/bar", gid: 100)

Unless follow_symlinks is set to true, then the owner symlink itself will be changed, otherwise the owner of the symlink destination file will be changed. For example, assuming symlinks as foo -> bar -> baz:

File.chown("foo", gid: 100)                        # changes foo's gid
File.chown("foo", gid: 100, follow_symlinks: true) # changes baz's gid

Deletes the file at path. Deleting non-existent file will raise an exception.

File.write("foo", "")
File.delete("./foo")
File.delete("./bar") # raises Errno (No such file or directory)

Returns true if the given path exists and is a directory.

File.write("foo", "")
Dir.mkdir("dir2")
File.directory?("foo")    # => false
File.directory?("dir2")   # => true
File.directory?("foobar") # => false

Returns all components of the given path except the last one.

File.dirname("/foo/bar/file.cr") # => "/foo/bar"

Yields each line in filename to the given block.

File.write("foobar", "foo\nbar")

array = [] of String
File.each_line("foobar") do |line|
  array << line
end
array # => ["foo", "bar"]

Returns true if the file at path is empty, otherwise returns false. Raises Errno if the file at path does not exist.

File.write("foo", "")
File.empty?("foo") # => true
File.write("foo", "foo")
File.empty?("foo") # => false

Returns true if path is executable by the real user id of this process else returns false.

File.write("foo", "foo")
File.executable?("foo") # => false

Returns true if path exists else returns false

File.delete("foo") if File.exists?("foo")
File.exists?("foo") # => false
File.write("foo", "foo")
File.exists?("foo") # => true

Converts path to an absolute path. Relative paths are referenced from the current working directory of the process unless dir is given, in which case it will be used as the starting point. "~" is expanded to the value passed to home. If it is false (default), home is not expanded. If true, it is expanded to the user's home directory (Path.home).

File.expand_path("foo")                 # => "/home/.../foo"
File.expand_path("~/foo", home: "/bar") # => "/bar/foo"
File.expand_path("baz", "/foo/bar")     # => "/foo/bar/baz"

Returns filename's extension, or an empty string if it has no extension.

File.extname("foo.cr") # => ".cr"

Returns true if given path exists and is a file.

File.write("foo", "")
Dir.mkdir("dir1")
File.file?("foo")    # => true
File.file?("dir1")   # => false
File.file?("foobar") # => false

Returns a File::Info object for the file given by path or raises Errno in case of an error.

If follow_symlinks is set (the default), symbolic links are followed. Otherwise, symbolic links return information on the symlink itself.

File.write("foo", "foo")
File.info("foo").size              # => 3
File.info("foo").modification_time # => 2015-09-23 06:24:19 UTC

File.symlink("foo", "bar")
File.info("bar", follow_symlinks: false).type.symlink? # => true

Returns a File::Info object for the file given by path or returns nil if the file does not exist.

If follow_symlinks is set (the default), symbolic links are followed. Otherwise, symbolic links return information on the symlink itself.

File.write("foo", "foo")
File.info?("foo").try(&.size) # => 3
File.info?("non_existent")    # => nil

File.symlink("foo", "bar")
File.info?("bar", follow_symlinks: false).try(&.type.symlink?) # => true

Returns a new string formed by joining the strings using File::SEPARATOR.

File.join({"foo", "bar", "baz"})       # => "foo/bar/baz"
File.join({"foo/", "/bar/", "/baz"})   # => "foo/bar/baz"
File.join(["/foo/", "/bar/", "/baz/"]) # => "/foo/bar/baz/"

Returns a new string formed by joining the strings using File::SEPARATOR.

File.join("foo", "bar", "baz")       # => "foo/bar/baz"
File.join("foo/", "/bar/", "/baz")   # => "foo/bar/baz"
File.join("/foo/", "/bar/", "/baz/") # => "/foo/bar/baz/"

Creates a new link (also known as a hard link) at new_path to an existing file given by old_path.

Matches path against pattern.

The pattern syntax is similar to shell filename globbing. It may contain the following metacharacters:

• * matches an unlimited number of arbitrary characters excluding /.
• "*" 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).
• ** matches an unlimited number of arbitrary characters including /.
• ? matches any one character excluding /.
• character sets:
• [abc] matches any one of these character.
• [^abc] matches any one character other than these.
• [a-z] matches any one character in the range.
• {a,b} matches subpattern a or b.
• \\ escapes the next character.

NOTE Only / is recognized as path separator in both pattern and path.

Opens the file named by filename. If a file is being created, its initial permissions may be set using the perm parameter. Then given block will be passed the opened file as an argument, the file will be automatically closed when the block returns.

See self.new for what mode can be.

Returns the content of filename as a string.

File.write("bar", "foo")
File.read("bar") # => "foo"

Returns all lines in filename as an array of strings.

File.write("foobar", "foo\nbar")
File.read_lines("foobar") # => ["foo", "bar"]

Returns true if path is readable by the real user id of this process else returns false.

File.write("foo", "foo")
File.readable?("foo") # => true

Returns value of a symbolic link .

Resolves the real path of path by following symbolic links.

Moves old_filename to new_filename.

File.write("afile", "foo")
File.exists?("afile") # => true

File.rename("afile", "afile.cr")
File.exists?("afile")    # => false
File.exists?("afile.cr") # => true

Returns true if path1 and path2 represents the same file. The comparison take symlinks in consideration if follow_symlinks is true.

Returns the size of the file at filename in bytes. Raises Errno if the file at filename does not exist.

File.size("foo") # raises Errno
File.write("foo", "foo")
File.size("foo") # => 3

Creates a symbolic link at new_path to an existing file given by old_path.

Returns true if the path is a symbolic link.

Creates a temporary file.

tempfile = File.tempfile("foo", ".bar")
tempfile.delete

prefix and suffix are appended to the front and end of the file name, respectively. These values may contain directory separators.

The file will be placed in dir which defaults to the standard temporary directory Dir.tempdir.

encoding and invalid are passed to IO#set_encoding.

It is the caller's responsibility to remove the file when no longer needed.

Creates a temporary file.

tempfile = File.tempfile(".bar")
tempfile.delete

prefix and suffix are appended to the front and end of the file name, respectively. These values may contain directory separators.

The file will be placed in dir which defaults to the standard temporary directory Dir.tempdir.

encoding and invalid are passed to IO#set_encoding.

It is the caller's responsibility to remove the file when no longer needed.

Creates a temporary file and yields it to the given block. It is closed and returned at the end of this method call.

tempfile = File.tempfile("foo", ".bar") do |file|
  file.print("bar")
end
File.read(tempfile.path) # => "bar"
tempfile.delete

prefix and suffix are appended to the front and end of the file name, respectively. These values may contain directory separators.

The file will be placed in dir which defaults to the standard temporary directory Dir.tempdir.

encoding and invalid are passed to IO#set_encoding.

It is the caller's responsibility to remove the file when no longer needed.

Creates a temporary file and yields it to the given block. It is closed and returned at the end of this method call.

tempfile = File.tempfile(".bar") do |file|
  file.print("bar")
end
File.read(tempfile.path) # => "bar"
tempfile.delete

prefix and suffix are appended to the front and end of the file name, respectively. These values may contain directory separators.

The file will be placed in dir which defaults to the standard temporary directory Dir.tempdir.

encoding and invalid are passed to IO#set_encoding.

It is the caller's responsibility to remove the file when no longer needed.

Returns a fully-qualified path to a temporary file. The file is not actually created on the file system.

File.tempname("foo", ".sock") # => "/tmp/foo20171206-1234-449386.sock"

prefix and suffix are appended to the front and end of the file name, respectively. These values may contain directory separators.

The path will be placed in dir which defaults to the standard temporary directory Dir.tempdir.

Returns a fully-qualified path to a temporary file. The optional suffix is appended to the file name.

File.tempname          # => "/tmp/20171206-1234-449386"
File.tempname(".sock") # => "/tmp/20171206-1234-449386.sock"

Attempts to set the access and modification times of the file named in the filename parameter to the value given in time.

If the file does not exist, it will be created.

Sets the access and modification times of filename.

Returns true if path is writable by the real user id of this process else returns false.

File.write("foo", "foo")
File.writable?("foo") # => true

Writes the given content to filename.

By default, an existing file will be overwritten.

filename will be created if it does not already exist.

File.write("foo", "bar")
File.write("foo", "baz", mode: "a")

NOTE If the content is a Slice(UInt8), those bytes will be written. If it's an IO, all bytes from the IO will be written. Otherwise, the string representation of content will be written (the result of invoking to_s on content).

See self.new for what mode can be.

Deletes this file.

Places an exclusive advisory lock. Only one process may hold an exclusive lock for a given file at a given time. Errno::EWOULDBLOCK is raised if blocking is set to false and any existing lock is set.

Places a shared advisory lock. More than one process may hold a shared lock for a given file at a given time. Errno::EWOULDBLOCK is raised if blocking is set to false and an existing exclusive lock is set.

Removes an existing advisory lock held by this process.

Flushes all data written to this File to the disk device so that all changed information can be retrieved even if the system crashes or is rebooted. The call blocks until the device reports that the transfer has completed. To reduce disk activity the flush_metadata parameter can be set to false, then the syscall fdatasync will be used and only data required for subsequent data retrieval is flushed. Metadata such as modified time and access time is not written.

Appends a String representation of this object which includes its class name, its object address and the values of all instance variables.

class Person
  def initialize(@name : String, @age : Int32)
  end
end

Person.new("John", 32).inspect # => #<Person:0x10fd31f20 @name="John", @age=32>

Yields an IO to read a section inside this file. Multiple sections can be read concurrently.

Returns the size in bytes of the currently opened file.

Truncates the file to the specified size. Requires that the current file is opened for writing.