method

atomic_write

v3.2.13 - Show latest stable - 0 notes - Class: File

atomic_write(file_name, temp_dir = Dir.tmpdir) public

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

Show source

# File activesupport/lib/active_support/core_ext/file/atomic.rb, line 15 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 begin # Get original file permissions old_stat = stat(file_name) rescue Errno::ENOENT # No old permissions, write a temp file to determine the defaults check_name = join(dirname(file_name), ".permissions_check.#{Thread.current.object_id}.#{Process.pid}.#{rand(1000000)}") open(check_name, "w") { } old_stat = stat(check_name) unlink(check_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

atomic_write

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