47 lines
1.6 KiB
Ruby
47 lines
1.6 KiB
Ruby
module ActiveSupport #:nodoc:
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module CoreExtensions #:nodoc:
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module File #:nodoc:
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module Atomic
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# Write to a file atomically. Useful for situations where you don't
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# want other processes or threads to see half-written files.
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#
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# File.atomic_write("important.file") do |file|
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# file.write("hello")
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# end
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#
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# If your temp directory is not on the same filesystem as the file you're
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# trying to write, you can provide a different temporary directory.
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#
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# File.atomic_write("/data/something.important", "/data/tmp") do |f|
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# file.write("hello")
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# end
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def atomic_write(file_name, temp_dir = Dir.tmpdir)
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require 'tempfile' unless defined?(Tempfile)
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temp_file = Tempfile.new(basename(file_name), temp_dir)
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yield temp_file
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temp_file.close
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begin
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# Get original file permissions
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old_stat = stat(file_name)
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rescue Errno::ENOENT
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# No old permissions, write a temp file to determine the defaults
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check_name = join(dirname(file_name), ".permissions_check.#{Thread.current.object_id}.#{Process.pid}.#{rand(1000000)}")
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open(check_name, "w") { }
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old_stat = stat(check_name)
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unlink(check_name)
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end
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# Overwrite original file with temp file
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rename(temp_file.path, file_name)
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# Set correct permissions on new file
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chown(old_stat.uid, old_stat.gid, file_name)
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chmod(old_stat.mode, file_name)
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end
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end
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end
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end
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end
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