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 it’s unnecessary to explicitly delete a Tempfile after use, though it’s a good practice to do so: not explicitly deleting unused Tempfiles can potentially leave behind a large number of temp files 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
Tempfile.create { … } exists for this purpose and is more convenient to use. Note that Tempfile.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.
# File tmp/rubies/ruby-3.1.3/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
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 Tempfile.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 Tempfile.new.
Tempfile.create('foo', '/home/temp') do |f| # ... do something with f ... end
# File tmp/rubies/ruby-3.1.3/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
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 Tempfile.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 Tempfile.new cannot find a unique filename within a limited number of tries, then it will raise an exception.
# File tmp/rubies/ruby-3.1.3/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
Creates a new Tempfile.
This method is not recommended and exists mostly for backward compatibility. Please use Tempfile.create instead, which avoids the cost of delegation, does not rely on a finalizer, and also unlinks the file when given a block.
Tempfile.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 Tempfile.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 Tempfile#close! or Tempfile#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 Tempfile.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
# File tmp/rubies/ruby-3.1.3/lib/tempfile.rb, line 168
def close(unlink_now=false)
_close
unlink if unlink_now
end
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 tmp/rubies/ruby-3.1.3/lib/tempfile.rb, line 175
def close!
close(true)
end
Closes and unlinks (deletes) the file. Has the same effect as called close(true).
# File tmp/rubies/ruby-3.1.3/lib/tempfile.rb, line 150
def open
_close
mode = @mode & ~(File::CREAT|File::EXCL)
@tmpfile = File.open(@tmpfile.path, mode, **@opts)
__setobj__(@tmpfile)
end
Opens or reopens the file with mode “r+”.
# File tmp/rubies/ruby-3.1.3/lib/tempfile.rb, line 228
def path
@unlinked ? nil : @tmpfile.path
end
Returns the full path name of the temporary file. This will be nil if unlink has been called.
# File tmp/rubies/ruby-3.1.3/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
Returns the size of the temporary file. As a side effect, the IO buffer is flushed before determining the size.
# File tmp/rubies/ruby-3.1.3/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
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