class method
self.atomic_write
Ruby on Rails edge
Since v3.0.20Signature
self.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
Parameters
-
file_namereq -
temp_diropt = dirname(file_name)
Source
# File activesupport/lib/active_support/core_ext/file/atomic.rb, line 26
def self.atomic_write(file_name, temp_dir = dirname(file_name))
old_stat = begin
File.stat(file_name)
rescue SystemCallError
nil
end
# Names can't be longer than 255B
tmp_suffix = ".tmp.#{SecureRandom.hex}"
tmp_name = ".#{basename(file_name).byteslice(0, 254 - tmp_suffix.bytesize)}#{tmp_suffix}"
tmp_path = File.join(temp_dir, tmp_name)
open(tmp_path, RDWR | CREAT | EXCL | SHARE_DELETE | BINARY) do |temp_file|
temp_file.binmode
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
return_val = yield temp_file
rescue => error
temp_file.close rescue nil
unlink(temp_file.path) rescue nil
raise error
else
rename(temp_file.path, file_name)
return_val
end
end
Defined in activesupport/lib/active_support/core_ext/file/atomic.rb line 26
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