diff options
Diffstat (limited to 'activesupport/lib/active_support/core_ext/file')
-rw-r--r-- | activesupport/lib/active_support/core_ext/file/atomic.rb | 46 |
1 files changed, 46 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/core_ext/file/atomic.rb b/activesupport/lib/active_support/core_ext/file/atomic.rb new file mode 100644 index 0000000000..4d3cf5423f --- /dev/null +++ b/activesupport/lib/active_support/core_ext/file/atomic.rb @@ -0,0 +1,46 @@ +require 'tempfile' + +module ActiveSupport #:nodoc: + module CoreExtensions #:nodoc: + module File #:nodoc: + module Atomic + # 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 + def atomic_write(file_name, 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 = ".permissions_check.#{Thread.current.object_id}.#{Process.pid}.#{rand(1000000)}" + new(check_name, "w") + old_stat = stat(check_name) + unlink(check_name) + end + + # Overwrite original file with temp file + rename(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 + end + end + end +end |