class File

• File
• IO::FileDescriptor
• IO
• Reference
• Object

Overview

A File instance represents a file entry in the local file system and allows using it as an IO.

file = File.new("path/to/file")
content = file.gets_to_end
file.close

# Implicit close with `open` and a block:
content = File.open("path/to/file") do |file|
  file.gets_to_end
end

# Shortcut of the above:
content = File.read("path/to/file")

# Write to a file by opening with a "write mode" specified.
File.open("path/to/file", "w") do |file|
  file.print "hello"
end
# Content of file on disk will now be "hello".

# Shortcut of the above:
File.write("path/to/file", "hello")

See new for various options mode can be.

Temporary Files

Every tempfile is operated as a File, including initializing, reading and writing.

tempfile = File.tempfile("foo")

File.size(tempfile.path)                   # => 6
File.info(tempfile.path).modification_time # => 2015-10-20 13:11:12 UTC
File.exists?(tempfile.path)                # => true
File.read_lines(tempfile.path)             # => ["foobar"]

Files created from tempfile are stored in a directory that handles temporary files (Dir.tempdir):

File.tempfile("foo").path # => "/tmp/foo.ulBCPS"

It is encouraged to delete a tempfile after using it, which ensures they are not left behind in your filesystem until garbage collected.

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

Included Modules

• Crystal::System::File

Defined in:

Class Method Summary

• .atomic_copy(src : String, dst : String, perm = DEFAULT_CREATE_PERMISSIONS) : Nil

  Ensures the copied file is written completely or not at all preventing corruption of the file.

• .atomic_replace(path : String, perm = DEFAULT_CREATE_PERMISSIONS, encoding = nil, invalid = nil, &block : IO::FileDescriptor, IO::FileDescriptor -> Nil) : Nil

  Allows reading from the original file and atomically replacing using #atomic_write.

• .atomic_write(path : Path | String, perm = DEFAULT_CREATE_PERMISSIONS, encoding = nil, invalid = nil, *, append : Bool = false, &block : IO::FileDescriptor -> Nil) : Nil

  Ensures the content written to the file descriptor is written completely or not at all preventing corruption of the file.

• .atomic_write(path : String, content, perm = DEFAULT_CREATE_PERMISSIONS, encoding = nil, invalid = nil) : Nil

  Writes the provided content completely or not at all preventing file corruption.

Class Method Detail