Module | ActiveSupport::CoreExtensions::File::Atomic |
In: |
vendor/rails/activesupport/lib/active_support/core_ext/file/atomic.rb
|
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 |f| file.write("hello") end
# File vendor/rails/activesupport/lib/active_support/core_ext/file/atomic.rb, line 18 18: def atomic_write(file_name, temp_dir = Dir.tmpdir) 19: require 'tempfile' unless defined?(Tempfile) 20: 21: temp_file = Tempfile.new(basename(file_name), temp_dir) 22: yield temp_file 23: temp_file.close 24: 25: begin 26: # Get original file permissions 27: old_stat = stat(file_name) 28: rescue Errno::ENOENT 29: # No old permissions, write a temp file to determine the defaults 30: check_name = join(dirname(file_name), ".permissions_check.#{Thread.current.object_id}.#{Process.pid}.#{rand(1000000)}") 31: open(check_name, "w") { } 32: old_stat = stat(check_name) 33: unlink(check_name) 34: end 35: 36: # Overwrite original file with temp file 37: rename(temp_file.path, file_name) 38: 39: # Set correct permissions on new file 40: chown(old_stat.uid, old_stat.gid, file_name) 41: chmod(old_stat.mode, file_name) 42: end