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
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¶ ↑
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
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.
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. The call returns the value of the block.
In any case, all arguments (
**options) will be treated as
Tempfile.create('foo', '/home/temp') do |f| # ... do something with f ... end
# File lib/tempfile.rb, line 327 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 with permissions 0600 (= only readable and writable by the owner) and opens it with mode “w+”.
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.
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')
Tempfile.new cannot find a unique filename within a limited number of tries, then it will raise an exception.
# File lib/tempfile.rb, line 126 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 new
If no block is given, this is a synonym for
If a block is given, then a
Tempfile object will be constructed, and the block is run with said object as argument. The
Tempfile object will be automatically closed after the block terminates. The call returns the value of the block.
In any case, all arguments (
*args) will be passed to
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 lib/tempfile.rb, line 290 def open(*args, **kw) tempfile = new(*args, **kw) if block_given? begin yield(tempfile) ensure tempfile.close end else tempfile end 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 lib/tempfile.rb, line 160 def close(unlink_now=false) _close unlink if unlink_now end
Closes and unlinks (deletes) the file. Has the same effect as called
# File lib/tempfile.rb, line 167 def close! close(true) end
Opens or reopens the file with mode “r+”.
# File lib/tempfile.rb, line 142 def open _close mode = @mode & ~(File::CREAT|File::EXCL) @tmpfile = File.open(@tmpfile.path, mode, @opts) __setobj__(@tmpfile) end
Returns the full path name of the temporary file. This will be nil if
unlink has been called.
# File lib/tempfile.rb, line 220 def path @unlinked ? nil : @tmpfile.path end
Returns the size of the temporary file. As a side effect, the
IO buffer is flushed before determining the size.
# File lib/tempfile.rb, line 226 def size if !@tmpfile.closed? @tmpfile.size # File#size calls rb_io_flush_raw() else File.size(@tmpfile.path) end end