Class | AtomicFile |
In: |
lib/facets/supplemental/facets/atomicfile.rb
|
Parent: | File |
This is a precursor to the possibility of a more extensive Atomic File I/O system. For now it simply provides a means for atomic file writing.
Write to a file atomically. Useful for situations where you don‘t want other processes or threads to see half-written files.
AtomicFile.write("tmp/important.file") do |file| file.write("hello") end
If your temporary directory is not on the same filesystem as the file you‘re trying to write, you can provide a different temporary directory.
AtomicFile.write("tmp/something.important", "tmp") do |file| file.write("hello") end
# File lib/facets/supplemental/facets/atomicfile.rb, line 23 def self.write(file_name, temp_dir=nil) temp_dir = temp_dir || Dir.tmpdir temp_file = Tempfile.new(basename(file_name), temp_dir) 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 chown(old_stat.uid, old_stat.gid, file_name) chmod(old_stat.mode, file_name) end