You can search for text using the grep command .
grep Text FileName
This is a sample of grep.
grep Foo foo.txt
You can specify multiple file names.
grep Text FileName1 FileName2
Search directory recursively
There is a "-r" option that allows you to search directories recursively. All files, including subdirectories, will be searched.
grep -r Text DirectoryName
There is a case-insensitive "-i" option.
# Both FOO and foo get caught grep -i foo filename
Use Perl regular expressions
This is an experimental feature of the Linux grep command, but with the "-P" option, you can use Perl regular expressions with grep. increase.
grep -P '^(foo|bar)$' filename