如何使用命令行工具根据固定宽度文本文件中特定内容的内容快速提取行？

I have a large text file (> 4 gb) which is in fixed-width format. I want to get a subset of that file based on content in specific columns. What would be the fastest way to do this?I have a large text file (> 4 gb) which is in f