whole_func_string: function ps(callback) {
    var args = ['-A', '-o', 'ppid,pid'];
  
    bin('ps', args, function(err, stdout, code) {
      if (err) return callback(err);
      if (code !== 0) {
        return callback(new Error('pidtree ps command exited with code ' + code));
      }
  
      // Example of stdout
      //
      // PPID   PID
      //    1   430
      //  430   432
      //    1   727
      //    1  7166
  
      try {
        stdout = stdout.split(os.EOL);
  
        var list = [];
        for (var i = 1; i < stdout.length; i++) {
          stdout[i] = stdout[i].trim();
          if (!stdout[i]) continue;
          stdout[i] = stdout[i].split(/\s+/);
          stdout[i][0] = parseInt(stdout[i][0], 10); // PPID
          stdout[i][1] = parseInt(stdout[i][1], 10); // PID
          list.push(stdout[i]);
        }
  
        callback(null, list);
      } catch (error) {
        callback(error);
      }
    });
  }
func_code_string: function ps(callback) {
    var args = ['-A', '-o', 'ppid,pid'];
  
    bin('ps', args, function(err, stdout, code) {
      if (err) return callback(err);
      if (code !== 0) {
        return callback(new Error('pidtree ps command exited with code ' + code));
      }
  
      // Example of stdout
      //
      // PPID   PID
      //    1   430
      //  430   432
      //    1   727
      //    1  7166
  
      try {
        stdout = stdout.split(os.EOL);
  
        var list = [];
        for (var i = 1; i < stdout.length; i++) {
          stdout[i] = stdout[i].trim();
          if (!stdout[i]) continue;
          stdout[i] = stdout[i].split(/\s+/);
          stdout[i][0] = parseInt(stdout[i][0], 10); // PPID
          stdout[i][1] = parseInt(stdout[i][1], 10); // PID
          list.push(stdout[i]);
        }
  
        callback(null, list);
      } catch (error) {
        callback(error);
      }
    });
  }
func_documentation_string: Gets the list of all the pids of the system through the ps command.
  @param  {Function} callback(err, list)