In WRLinux 8 project, grep tool can not support -P parameter, which was used to support Perl regular expression. The grep version in WRLinux 8 is 2.21, in it's release notes, it show -P still can be used. But in WRLinux 4.3, the grep(2.5.1) can support -P parameter.
Build a WRLinux 8 x86 project, and step into $(prj_dir)/export/dist/bin run the following command: ./grep.grep -o -P 'PATTERN' file then it will show: ./grep.grep: support for the -P option is not compiled into this --disable-perl-regexp binary In a WRLinux 4.3 project, the same command can work well.
