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Versions: 6
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Stored size: 1.59 KB
Contents
require 'thread' unless defined?(Thread)
require 'tempfile' unless defined?(Tempfile)
require 'fileutils' unless defined?(FileUtils)
# 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.
class AtomicFile < File
# 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
#
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
end
Version data entries
6 entries across 5 versions & 1 rubygems