grep 忽略大小写查找某一个路径下某一文件类型中的字符串

grep -i "search_string"  /search/dir -r --include=*.txt

If want to search in different file types, just use:

grep -i "search_string"  /search/dir -r --include=*.txt --include=*.cpp --include=*.h

 

Search string1 or string 2 with pipe:

cat file | grep -E "string1|string2"