summaryrefslogtreecommitdiff
path: root/lib/tempfile.rb
blob: 671ac7b83beb32090a6b7596b643b4b8f89283a4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
# frozen_string_literal: true
#
# tempfile - manipulates temporary files
#
# $Id$
#

require 'delegate'
require 'tmpdir'

# 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
#
# === 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 Tempfile < DelegateClass(File)
  # call-seq:
  #    new(basename = "", [tmpdir = Dir.tmpdir], [options])
  #
  # 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 $SAFE > 0 and the given +tmpdir+ is tainted, it uses
  # '/tmp' as the temporary directory. Please note that ENV values
  # are tainted by default, and +Dir.tmpdir+'s return value might
  # come from environment variables (e.g. <tt>$TMPDIR</tt>).
  #
  #   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 Tempfile.new cannot find a unique filename within a limited
  # number of tries, then it will raise an exception.
  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

  # Opens or reopens the file with mode "r+".
  def open
    _close
    mode = @mode & ~(File::CREAT|File::EXCL)
    @tmpfile = File.open(@tmpfile.path, mode, @opts)
    __setobj__(@tmpfile)
  end

  def _close    # :nodoc:
    @tmpfile.close
  end
  protected :_close

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

  # Closes and unlinks (deletes) the file. Has the same effect as called
  # <tt>close(true)</tt>.
  def close!
    close(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
  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
  alias delete unlink

  # Returns the full path name of the temporary file.
  # This will be nil if #unlink has been called.
  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.
  def size
    if !@tmpfile.closed?
      @tmpfile.size # File#size calls rb_io_flush_raw()
    else
      File.size(@tmpfile.path)
    end
  end
  alias length size

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

  class Remover
    def initialize(tmpfile)
      @pid = Process.pid
      @tmpfile = tmpfile
    end

    def call(*args)
      return if @pid != Process.pid

      $stderr.puts "removing #{@tmpfile.path}..." if $DEBUG

      @tmpfile.close
      begin
        File.unlink(@tmpfile.path)
      rescue Errno::ENOENT
      end

      $stderr.puts "done" if $DEBUG
    end
  end

  class << self
    # :startdoc:

    # Creates a new Tempfile.
    #
    # 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 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 (<code>*args</code>) 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
    def open(*args)
      tempfile = new(*args)

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

# Creates a temporary file as usual File object (not Tempfile).
# It doesn't use finalizer and delegation.
#
# If no block is given, this is similar to Tempfile.new except
# creating File instead of Tempfile.
# 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.
# The call returns the value of the block.
#
# In any case, all arguments (+basename+, +tmpdir+, +mode+, and
# <code>**options</code>) will be treated as Tempfile.new.
#
#   Tempfile.create('foo', '/home/temp') do |f|
#      ... do something with f ...
#   end
#
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