class File
Public Class Methods
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
If your temp directory is not on the same filesystem as the file you're trying to write, you can provide a different temporary directory.
File.atomic_write('/data/something.important', '/data/tmp') do |file|
file.write('hello')
end
# File activesupport/lib/active_support/core_ext/file/atomic.rb, line 17
def self.atomic_write(file_name, temp_dir = Dir.tmpdir)
require 'tempfile' unless defined?(Tempfile)
require 'fileutils' unless defined?(FileUtils)
temp_file = Tempfile.new(basename(file_name), temp_dir)
temp_file.binmode
yield temp_file
temp_file.close
if File.exist?(file_name)
# Get original file permissions
old_stat = stat(file_name)
else
# If not possible, probe which are the default permissions in the
# destination directory.
old_stat = probe_stat_in(dirname(file_name))
end
# Overwrite original file with temp file
FileUtils.mv(temp_file.path, file_name)
# Set correct permissions on new file
begin
chown(old_stat.uid, old_stat.gid, file_name)
# This operation will affect filesystem ACL's
chmod(old_stat.mode, file_name)
rescue Errno::EPERM
# Changing file ownership failed, moving on.
end
end© 2004–2016 David Heinemeier Hansson
Licensed under the MIT License.