在命令行中使用正则表达式的grep

Question

I'm interested in finding pattern like %CHILD_NAME%, %PARENT_NAME%, %ADDRESS% using regex and preferably recursively in the current directory Following is the grep command I am using

grep -r "(.[A-Z]+[_]*[A-Z]+%)" *

When I use the same regex above at http://www.regexr.com , it does match %CHILD_NAME% but my command is not able to find this pattern in any file in current or sub directory.

Answer 1

By default, grep uses basic regular expression and meta-characters like + lose their meaning and need to be escaped. Remove the capturing group ( ) , escape the + quantifiers and use an actual % in place of .

grep -r '%[A-Z]\+[_]*[A-Z]\+%' *

Although, you could probably use the following:

grep -r "%[A-Z_]\+%" *

Answer 2

First of all, you regex is too generic: at matches CHILD_NAME% (without % in the front) as well. A better regex is:

"%[A-Z]+(_[A-Z]+)*%"

Next, it is advisable to use the perl interpretation of regexes using the -P flag:

grep -r -P "%[A-Z]+(_[A-Z]+)*%" .

You can also use the -E flag here (extensive mode).