Answer by J G Miller for Prevent parameter expansion in shell script

You need to familiarize yourself with the basic rules concerning shell expansion of variables.

NAME="start"

IF you present $NAME to the shell it will be exanded to the string start

If you put single quotes around a string, the shell does not expand whatever is within the single quotes, so '$NAME' stays as $NAME

Now with double quotes, the shell expands the variable $NAME to the string start but the double quotes prevent what is known as file globbing.

What is file globbing you ask?

Well it you do

ls -l *

you expect the ls command to list all of the files. It is not ls which is converting * to all of the file names in the directory, but the shell.

Now say you had a file named * in your directory and you just wanted to list that file, then you could use either

ls -l '*' 

or

ls -l "*"

and both the single and double quotes prevent the shell from expanding the * to the list of files.

Globbing can also be turned off by doing

set noglob

Rather than having this simple find string as a separate shell script requiring a new shell to be invoked every time it is used, the more efficient way is to create is as a shell function fs (find_string)

function fs ()
{
 \find . -type f -name "${1}" -exec egrep --color "${2}" {} /dev/null \;
}