File.html

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            <span>Ruby on Rails 8.0.0</span><br />
        
        <div class="type">Class</div>
        <h1>
            File
            
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                    <a href="Object.html">Object</a>
                    
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        <ul class="files">
            
            <li><a href="../files/activesupport/lib/active_support/core_ext/file/atomic_rb.html">activesupport/lib/active_support/core_ext/file/atomic.rb</a></li>
            
            <li><a href="../files/railties/lib/rails/commands/credentials/credentials_command/diffing_rb.html">railties/lib/rails/commands/credentials/credentials_command/diffing.rb</a></li>
            
            <li><a href="../files/railties/lib/rails/generators/app_base_rb.html">railties/lib/rails/generators/app_base.rb</a></li>
            
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    <h2 id="methods">Methods</h2>
    <ul>
      
        <li>
          <a href="#method-c-atomic_write">atomic_write</a>
        </li>
      
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    <!-- Methods -->
    
      <h2 id="class-public-methods">Class Public methods</h2>
      
        <div class="method">
          <h3 id="method-c-atomic_write">
            
              atomic_write(file_name, temp_dir = dirname(file_name))
            
          </h3>

          
            <div class="description">
              <p>Write to a file atomically. Useful for situations where you don’t want other processes or threads to see half-written files.</p>

<pre><code>File.atomic_write(&#39;important.file&#39;) do |file|
  file.write(&#39;hello&#39;)
end
</code></pre>

<p>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.</p>

<pre><code>File.atomic_write(&#39;/data/something.important&#39;, &#39;/data/tmp&#39;) do |file|
  file.write(&#39;hello&#39;)
end
</code></pre>
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            <details class="method__source">
              <summary>
                <span class="label">📝 Source code</span>
              </summary>

              <pre><code class="ruby"># File activesupport/lib/active_support/core_ext/file/atomic.rb, line 21
  def self.atomic_write(file_name, temp_dir = dirname(file_name))
    require &quot;tempfile&quot; unless defined?(Tempfile)

    Tempfile.open(&quot;.#{basename(file_name)}&quot;, 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&#39;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</code></pre>
              
                <a href="https://github.com/rails/rails/blob/dd8f7185faeca6ee968a6e9367f6d8601a83b8db/activesupport/lib/active_support/core_ext/file/atomic.rb#L21" target="_blank" class="github_url">🔎 See on GitHub</a>
              
            </details>
          
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