Useful Linux Commands

The command:

$ grep "pattern" existingDirectory

stands for 'global regular expression print' and outputs the names of the files where pattern, which is either a simple search string or some regular expression, is present within the existingDirectory folder. For example, entering grep "Bla Bla!" * will show all the files in the current directory where the string Bla Bla! is present. This is because the * symbol is a 'wild-card' that selects all the files in the current directory for this search. The grep command has many useful command-line options, which you can learn more about in the man grep or info grep manual pages.

Many examples of using grep are brought at https://www.thegeekstuff.com/2009/03/15-practical-unix-grep-command-examples/.