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Tempfile

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 existance 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

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.

Public Class Methods

new(basename, [tmpdir = Dir.tmpdir], [options]) click to toggle source

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

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. When $SAFE > 0 and the given tmpdir is tainted, it uses ‘/tmp’ as the temporary directory. Please note that ENV values are tainted by default, and Dir.tmpdir‘s return value might come from environment variables (e.g. $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')

Exceptions

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

 
               # File tempfile.rb, line 129
def initialize(basename, *rest)
  @data = []
  @clean_proc = Remover.new(@data)
  ObjectSpace.define_finalizer(self, @clean_proc)

  create(basename, *rest) do |tmpname, n, opts|
    lock = tmpname + '.lock'
    mode = File::RDWR|File::CREAT|File::EXCL
    perm = 0600
    if opts
      mode |= opts.delete(:mode) || 0
      opts[:perm] = perm
      perm = nil
    else
      opts = perm
    end
    self.class.mkdir(lock)
    begin
      @data[1] = @tmpfile = File.open(tmpname, mode, opts)
      @data[0] = @tmpname = tmpname
    ensure
      self.class.rmdir(lock)
    end
    @mode = mode & ~(File::CREAT|File::EXCL)
    perm or opts.freeze
    @opts = opts
  end

  super(@tmpfile)
end
            

Public Instance Methods

close(unlink_now=false) click to toggle source

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.

 
               # File tempfile.rb, line 181
def close(unlink_now=false)
  if unlink_now
    close!
  else
    _close
  end
end
            
close!() click to toggle source

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

 
               # File tempfile.rb, line 191
def close!
  _close
  unlink
  ObjectSpace.undefine_finalizer(self)
end
            
delete() click to toggle source
Alias for: unlink
length() click to toggle source
Alias for: size
mkdir(*args) click to toggle source
 
               # File tempfile.rb, line 329
def mkdir(*args)
  Dir.mkdir(*args)
end
            
open() click to toggle source

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

 
               # File tempfile.rb, line 161
def open
  @tmpfile.close if @tmpfile
  @tmpfile = File.open(@tmpname, @mode, @opts)
  @data[1] = @tmpfile
  __setobj__(@tmpfile)
end
            
path() click to toggle source

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

 
               # File tempfile.rb, line 248
def path
  @tmpname
end
            
rmdir(*args) click to toggle source
 
               # File tempfile.rb, line 332
def rmdir(*args)
  Dir.rmdir(*args)
end
            
size() click to toggle source

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

 
               # File tempfile.rb, line 254
def size
  if @tmpfile
    @tmpfile.flush
    @tmpfile.stat.size
  elsif @tmpname
    File.size(@tmpname)
  else
    0
  end
end
            
Also aliased as: length

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