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 lib/active_support/core_ext/file/atomic.rb, line 15 15: def self.atomic_write(file_name, temp_dir = Dir.tmpdir) 16: require 'tempfile' unless defined?(Tempfile) 17: require 'fileutils' unless defined?(FileUtils) 18: 19: temp_file = Tempfile.new(basename(file_name), temp_dir) 20: yield temp_file 21: temp_file.close 22: 23: begin 24: # Get original file permissions 25: old_stat = stat(file_name) 26: rescue Errno::ENOENT 27: # No old permissions, write a temp file to determine the defaults 28: check_name = join(dirname(file_name), ".permissions_check.#{Thread.current.object_id}.#{Process.pid}.#{rand(1000000)}") 29: open(check_name, "w") { } 30: old_stat = stat(check_name) 31: unlink(check_name) 32: end 33: 34: # Overwrite original file with temp file 35: FileUtils.mv(temp_file.path, file_name) 36: 37: # Set correct permissions on new file 38: chown(old_stat.uid, old_stat.gid, file_name) 39: chmod(old_stat.mode, file_name) 40: end
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