以较便宜的方式搜索大型文本文件中的字符串

I need to search a pretty large text file for a particular string. Its a build log with about 5000 lines of text. Whats the best way to go about doing that? Using regex shouldn't cause any problems should it? I'll go ahead and read blocks of lines, and use the simple find.I need to search a pretty large text file for a