现有大批量的文本数据，需要截取其中符合一定范围的数据（减少数据量）。数据的格式如下：
42.69,-84.6,1
41.74,-86.21,1
42.26,-83.73,2
43.01,-83.68,6
42.74,-84.48,3
42.29,-83.7,4
42.29,-83.25,2
41.36,-82.07,1
42.99,-83.73,3
42.24,-84.41,1
其中，截取的目标范围是第一列的数字在一定范围，如40-44，第二列在另个范围。
开始我是将其全部导入到数据库中（copy命令），然后再进行delete操作，但随数据的处理，数据库的速度越来越慢，导致数据的处理速度不可接受。因此想在入库前就先行截取。Google后发现了解决方案：Using AWK to Filter Rows。
具体解决方案如下：
awk -F',' '{ if($1 <= 44.0 && $1>=41.0 && $2<=-82.0 && $2>=-87.0) {print }}' 20161026-2300-point.csv
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