• This the most powerful and useful command in all of Unix (IMHO) is the find command. It will explore all subdirectories at a specified root location and perform a command on all files. 
• Here is a command to find the word "California" inside any text file (and some binary files) underneath the current directory.
• Find all files under my current working directory (cwd) with the word California in the file.

$ find . -type f -exec grep California {} \; -print

• The command "prints" to the screen (sysout), not a printer.
• The "-type f" means to only look at files.  Otherwise you will get an error reported for all directories (-type d) traversed.
• The "{} \; -print" is voodoo.  Just go with it.
• How many lines were there in the results?

$ find . -type f -exec grep California {} \; -print | wc -l 

• Line numbers please

$ find . -type f -exec grep -n California {} \; -print | wc -l 

• I want both upper case and lower (California and california)

$ find . -type f -exec grep -i California {} \; -print | wc -l 

• Just my log file over in first logs

$ find /etc/logs/Server.log -exec grep Error {} \; -print

• Too much output!  Show me only lines in the file with both "California" and "surfboard".  I want the output to go to a file. Note you will lose filenames (unless they have "surfboard" in their name.)

$find . -type f -exec grep California {} \; -print | grep surfboard > SurfsUp.txt

• The find command can be used to run most any unix command.  I have only shown "greg".  You could delete files with "rm" and much more.  Search for "cygwin find" to see more.
• Sorry no examples.