Class: Tempfile

Relationships & Source Files
Namespace Children
Classes: `Remover`
Super Chains via Extension / Inclusion / Inheritance
Class Chain: self, File
Instance Chain: self, File
Inherits:	File Object File Tempfile
Defined in:	lib/tempfile.rb

Overview

A utility class for managing temporary files. When you create a Tempfile object, it will create a temporary file with a unique filename. A Tempfile objects behaves just like a File object, and you can perform all the usual file operations on it: reading data, writing data, changing its permissions, etc. So although this class does not explicitly document all instance methods supported by File, you can in fact call any File instance method on a Tempfile object.

Synopsis

require 'tempfile'

file = Tempfile.new('foo')
file.path      # => A unique filename in the OS's temp directory,
               #    e.g.: "/tmp/foo.24722.0"
               #    This filename contains 'foo' in its basename.
file.write("hello world")
file.rewind
file.read      # => "hello world"
file.close
file.unlink    # deletes the temp file

Good practices

Explicit close

When a Tempfile object is garbage collected, or when the Ruby interpreter exits, its associated temporary file is automatically deleted. This means that’s it’s unnecessary to explicitly delete a Tempfile after use, though it’s good practice to do so: not explicitly deleting unused Tempfiles can potentially leave behind large amounts of tempfiles on the filesystem until they’re garbage collected. The existence of these temp files can make it harder to determine a new Tempfile filename.

Therefore, one should always call #unlink or close in an ensure block, like this:

file = Tempfile.new('foo')
begin
   # ...do something with file...
ensure
   file.close
   file.unlink   # deletes the temp file
end

.create { … } exists for this purpose and is more convenient to use. Note that .create returns a File instance instead of a Tempfile, which also avoids the overhead and complications of delegation.

Tempfile.open('foo') do |file|
   # ...do something with file...
end

Unlink after creation

On POSIX systems, it’s possible to unlink a file right after creating it, and before closing it. This removes the filesystem entry without closing the file handle, so it ensures that only the processes that already had the file handle open can access the file’s contents. It’s strongly recommended that you do this if you do not want any other processes to be able to read from or write to the Tempfile, and you do not need to know the Tempfile’s filename either.

For example, a practical use case for unlink-after-creation would be this: you need a large byte buffer that’s too large to comfortably fit in RAM, e.g. when you’re writing a web server and you want to buffer the client’s file upload data.

Please refer to #unlink for more information and a code example.

Minor notes

Tempfile’s filename picking method is both thread-safe and inter-process-safe: it guarantees that no other threads or processes will pick the same filename.

Tempfile itself however may not be entirely thread-safe. If you access the same Tempfile object from multiple threads then you should protect it with a mutex.

Class Method Summary

.create(basename = "", tmpdir = nil, mode: 0, **options)

Creates a temporary file as a usual File object (not a Tempfile).
.new(basename = "", tmpdir = nil, mode: 0, **options) ⇒ Tempfile constructor

Creates a temporary file with permissions 0600 (= only readable and writable by the owner) and opens it with mode “w+”.
.open(*args, **kw)

Creates a new Tempfile.

Instance Method Summary

#close(unlink_now = false)

Closes the file.
#close!

Closes and unlinks (deletes) the file.
#delete

Alias for #unlink.
#length

Alias for #size.
#open

Opens or reopens the file with mode “r+”.
#path

Returns the full path name of the temporary file.
#size (also: #length)

Returns the size of the temporary file.
#unlink (also: #delete)

Unlinks (deletes) the file from the filesystem.
#inspect Internal use only
#_close protected Internal use only

Constructor Details

.new(basename = "", tmpdir = nil, mode: 0, **options) ⇒ `Tempfile`

Creates a temporary file with permissions 0600 (= only readable and writable by the owner) and opens it with mode “w+”.

It is recommended to use .create { … } instead when possible, because that method avoids the cost of delegation and does not rely on a finalizer to close and unlink the file, which is unreliable.

The basename parameter is used to determine the name of the temporary file. You can either pass a String or an Array with 2 String elements. In the former form, the temporary file’s base name will begin with the given string. In the latter form, the temporary file’s base name will begin with the array’s first element, and end with the second element. For example:

file = Tempfile.new('hello')
file.path  # => something like: "/tmp/hello2843-8392-92849382--0"

# Use the Array form to enforce an extension in the filename:
file = Tempfile.new(['hello', '.jpg'])
file.path  # => something like: "/tmp/hello2843-8392-92849382--0.jpg"

The temporary file will be placed in the directory as specified by the tmpdir parameter. By default, this is Dir.tmpdir.

file = Tempfile.new('hello', '/home/aisaka')
file.path  # => something like: "/home/aisaka/hello2843-8392-92849382--0"

You can also pass an options hash. Under the hood, Tempfile creates the temporary file using File.open. These options will be passed to File.open. This is mostly useful for specifying encoding options, e.g.:

Tempfile.new('hello', '/home/aisaka', encoding: 'ascii-8bit')

# You can also omit the 'tmpdir' parameter:
Tempfile.new('hello', encoding: 'ascii-8bit')

Note: mode keyword argument, as accepted by Tempfile, can only be numeric, combination of the modes defined in File::Constants.

Exceptions

If new cannot find a unique filename within a limited number of tries, then it will raise an exception.

[ GitHub ]

# File 'lib/tempfile.rb', line 134


def initialize(basename="", tmpdir=nil, mode: 0, **options)
  warn "Tempfile.new doesn't call the given block.", uplevel: 1 if block_given?

  @unlinked = false
  @mode = mode|File::RDWR|File::CREAT|File::EXCL
  ::Dir::Tmpname.create(basename, tmpdir, **options) do |tmpname, n, opts|
    opts[:perm] = 0600
    @tmpfile = File.open(tmpname, @mode, **opts)
    @opts = opts.freeze
  end
  ObjectSpace.define_finalizer(self, Remover.new(@tmpfile))

  super(@tmpfile)
end

Class Method Details

.create(basename = "", tmpdir = nil, mode: 0, **options)

Creates a temporary file as a usual File object (not a Tempfile). It does not use finalizer and delegation, which makes it more efficient and reliable.

If no block is given, this is similar to .new except creating File instead of Tempfile. In that case, the created file is not removed automatically. You should use File.unlink to remove it.

If a block is given, then a File object will be constructed, and the block is invoked with the object as the argument. The File object will be automatically closed and the temporary file is removed after the block terminates, releasing all resources that the block created. The call returns the value of the block.

In any case, all arguments (basename, tmpdir, mode, and **options) will be treated the same as for .new.

Tempfile.create('foo', '/home/temp') do |f|
   # ... do something with f ...
end

[ GitHub ]

# File 'lib/tempfile.rb', line 349


def Tempfile.create(basename="", tmpdir=nil, mode: 0, **options)
  tmpfile = nil
  Dir::Tmpname.create(basename, tmpdir, **options) do |tmpname, n, opts|
    mode |= File::RDWR|File::CREAT|File::EXCL
    opts[:perm] = 0600
    tmpfile = File.open(tmpname, mode, **opts)
  end
  if block_given?
    begin
      yield tmpfile
    ensure
      unless tmpfile.closed?
        if File.identical?(tmpfile, tmpfile.path)
          unlinked = File.unlink tmpfile.path rescue nil
        end
        tmpfile.close
      end
      unless unlinked
        begin
          File.unlink tmpfile.path
        rescue Errno::ENOENT
        end
      end
    end
  else
    tmpfile
  end
end

.open(*args, **kw)

Creates a new Tempfile.

This method is not recommended and exists mostly for backward compatibility. Please use .create instead, which avoids the cost of delegation, does not rely on a finalizer, and also unlinks the file when given a block.

open is still appropriate if you need the Tempfile to be unlinked by a finalizer and you cannot explicitly know where in the program the Tempfile can be unlinked safely.

If no block is given, this is a synonym for .new.

If a block is given, then a Tempfile object will be constructed, and the block is run with the Tempfile object as argument. The Tempfile object will be automatically closed after the block terminates. However, the file will not be unlinked and needs to be manually unlinked with #close! or #unlink. The finalizer will try to unlink but should not be relied upon as it can keep the file on the disk much longer than intended. For instance, on CRuby, finalizers can be delayed due to conservative stack scanning and references left in unused memory.

The call returns the value of the block.

In any case, all arguments (*args) will be passed to .new.

Tempfile.open('foo', '/home/temp') do |f|
   # ... do something with f ...
end

# Equivalent:
f = Tempfile.open('foo', '/home/temp')
begin
   # ... do something with f ...
ensure
   f.close
end

[ GitHub ]

# File 'lib/tempfile.rb', line 312


def open(*args, **kw)
  tempfile = new(*args, **kw)

  if block_given?
    begin
      yield(tempfile)
    ensure
      tempfile.close
    end
  else
    tempfile
  end
end

Instance Method Details

#_close (protected)

This method is for internal use only.

[ GitHub ]

# File 'lib/tempfile.rb', line 157


def _close    # :nodoc:
  @tmpfile.close
end

#close(unlink_now = false)

Closes the file. If unlink_now is true, then the file will be unlinked (deleted) after closing. Of course, you can choose to later call #unlink if you do not unlink it now.

If you don’t explicitly unlink the temporary file, the removal will be delayed until the object is finalized.

[ GitHub ]

# File 'lib/tempfile.rb', line 168


def close(unlink_now=false)
  _close
  unlink if unlink_now
end

#close!

Closes and unlinks (deletes) the file. Has the same effect as called close(true).

[ GitHub ]

# File 'lib/tempfile.rb', line 175


def close!
  close(true)
end

#delete

Alias for #unlink.

[ GitHub ]

# File 'lib/tempfile.rb', line 224


alias delete unlink

#inspect

This method is for internal use only.

[ GitHub ]

# File 'lib/tempfile.rb', line 244


def inspect
  if @tmpfile.closed?
    "#<#{self.class}:#{path} (closed)>"
  else
    "#<#{self.class}:#{path}>"
  end
end

#length

Alias for #size.

[ GitHub ]

# File 'lib/tempfile.rb', line 241


alias length size

#open

Opens or reopens the file with mode “r+”.

[ GitHub ]

# File 'lib/tempfile.rb', line 150


def open
  _close
  mode = @mode & ~(File::CREAT|File::EXCL)
  @tmpfile = File.open(@tmpfile.path, mode, **@opts)
  __setobj__(@tmpfile)
end

#path

Returns the full path name of the temporary file. This will be nil if #unlink has been called.

[ GitHub ]

# File 'lib/tempfile.rb', line 228


def path
  @unlinked ? nil : @tmpfile.path
end

#size Also known as: #length

Returns the size of the temporary file. As a side effect, the IO buffer is flushed before determining the size.

[ GitHub ]

# File 'lib/tempfile.rb', line 234


def size
  if !@tmpfile.closed?
    @tmpfile.size # File#size calls rb_io_flush_raw()
  else
    File.size(@tmpfile.path)
  end
end

#unlink Also known as: #delete

Unlinks (deletes) the file from the filesystem. One should always unlink the file after using it, as is explained in the “Explicit close” good practice section in the Tempfile overview:

file = Tempfile.new('foo')
begin
   # ...do something with file...
ensure
   file.close
   file.unlink   # deletes the temp file
end

Unlink-before-close

On POSIX systems it’s possible to unlink a file before closing it. This practice is explained in detail in the Tempfile overview (section “Unlink after creation”); please refer there for more information.

However, unlink-before-close may not be supported on non-POSIX operating systems. Microsoft Windows is the most notable case: unlinking a non-closed file will result in an error, which this method will silently ignore. If you want to practice unlink-before-close whenever possible, then you should write code like this:

file = Tempfile.new('foo')
file.unlink   # On Windows this silently fails.
begin
   # ... do something with file ...
ensure
   file.close!   # Closes the file handle. If the file wasn't unlinked
                 # because #unlink failed, then this method will attempt
                 # to do so again.
end

[ GitHub ]

# File 'lib/tempfile.rb', line 212


def unlink
  return if @unlinked
  begin
    File.unlink(@tmpfile.path)
  rescue Errno::ENOENT
  rescue Errno::EACCES
    # may not be able to unlink on Windows; just ignore
    return
  end
  ObjectSpace.undefine_finalizer(self)
  @unlinked = true
end

Class: Tempfile

Overview

Synopsis

Good practices

Explicit close

Unlink after creation

Minor notes

Class Method Summary

Instance Method Summary

Constructor Details

.new(basename = "", tmpdir = nil, mode: 0, **options) ⇒ Tempfile

Exceptions

Class Method Details

.create(basename = "", tmpdir = nil, mode: 0, **options)

.open(*args, **kw)

Instance Method Details

#_close (protected)

#close(unlink_now = false)

#close!

#delete

#inspect

#length

#open

#path

#size Also known as: #length

#unlink Also known as: #delete

Unlink-before-close

.new(basename = "", tmpdir = nil, mode: 0, **options) ⇒ `Tempfile`