class File
Public class methods
atomic_write(file_name, temp_dir = dirname(file_name))
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
This method needs to create a temporary file. By default it will create it in the same directory as the destination file. If you don’t like this behavior you can provide a different directory but it must be on the same physical filesystem as the file you’re trying to write.
File.atomic_write('/data/something.important', '/data/tmp') do |file|
file.write('hello')
end
Source code GitHub
# File activesupport/lib/active_support/core_ext/file/atomic.rb, line 21
def self.atomic_write(file_name, temp_dir = dirname(file_name))
require "tempfile" unless defined?(Tempfile)
Tempfile.open(".#{basename(file_name)}", temp_dir) do |temp_file|
temp_file.binmode
return_val = yield temp_file
temp_file.close
old_stat = if exist?(file_name)
# Get original file permissions
stat(file_name)
else
# If not possible, probe which are the default permissions in the
# destination directory.
probe_stat_in(dirname(file_name))
end
if old_stat
# Set correct permissions on new file
begin
chown(old_stat.uid, old_stat.gid, temp_file.path)
# This operation will affect filesystem ACL's
chmod(old_stat.mode, temp_file.path)
rescue Errno::EPERM, Errno::EACCES
# Changing file ownership failed, moving on.
end
end
# Overwrite original file with temp file
rename(temp_file.path, file_name)
return_val
end
end