Class: File
Class Method Summary collapse
-
.atomic_write(file_name, temp_dir = dirname(file_name)) ⇒ Object
Write to a file atomically.
-
.probe_stat_in(dir) ⇒ Object
Private utility method.
Class Method Details
.atomic_write(file_name, temp_dir = dirname(file_name)) ⇒ Object
Write to a file atomically. Useful for situations where you don’t want other processes or threads to see half-written files.
File.atomic_write('important.file') do |file|
file.write('hello')
end
This method needs to create a temporary file. By default it will create it in the same directory as the destination file. If you don’t like this behavior you can provide a different directory but it must be on the same physical filesystem as the file you’re trying to write.
File.atomic_write('/data/something.important', '/data/tmp') do |file|
file.write('hello')
end
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# File 'lib/active_support/core_ext/file/atomic.rb', line 21 def self.atomic_write(file_name, temp_dir = dirname(file_name)) require "tempfile" unless defined?(Tempfile) Tempfile.open(".#{basename(file_name)}", temp_dir) do |temp_file| temp_file.binmode return_val = yield temp_file temp_file.close old_stat = if exist?(file_name) # Get original file permissions stat(file_name) else # If not possible, probe which are the default permissions in the # destination directory. probe_stat_in(dirname(file_name)) end if old_stat # Set correct permissions on new file begin chown(old_stat.uid, old_stat.gid, temp_file.path) # This operation will affect filesystem ACL's chmod(old_stat.mode, temp_file.path) rescue Errno::EPERM, Errno::EACCES # Changing file ownership failed, moving on. end end # Overwrite original file with temp file rename(temp_file.path, file_name) return_val end end |
.probe_stat_in(dir) ⇒ Object
Private utility method.
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# File 'lib/active_support/core_ext/file/atomic.rb', line 56 def self.probe_stat_in(dir) # :nodoc: basename = [ ".permissions_check", Thread.current.object_id, Process.pid, rand(1000000) ].join(".") file_name = join(dir, basename) FileUtils.touch(file_name) stat(file_name) ensure FileUtils.rm_f(file_name) if file_name end |