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, Errno::EACCES # Changing file ownership failed, moving on. end end