How can I count the occurrences of a string within a file?

I'm taking some guesses here, because I don't quite understand what you're asking.

I think that what you want is a count of the number of lines on which the pattern 'echo' appears in the given file.

I've pasted your sample text into a file called 6741967.

First, grep finds the matches:

james@Brindle:tmp$grep echo 6741967 
    echo "Preparing to add a new user..."
echo "1. Add user"
echo "2. Exit"
echo "Enter your choice: "

Second, use wc -l to count the lines

james@Brindle:tmp$grep echo 6741967  | wc -l
       4

The number of string occurrences (not lines) can be obtained using grep with -o option and wc (word count):

$ echo "echo 1234 echo" | grep -o echo
echo
echo
$ echo "echo 1234 echo" | grep -o echo | wc -l
2

So the full solution for your problem would look like this:

$ grep -o "echo" FILE | wc -l

This will output the number of lines that contain your search string.

grep -c "echo" FILE

This won't, however, count the number of occurrences in the file (ie, if you have echo multiple times on one line).

edit:

After playing around a bit, you could get the number of occurrences using this dirty little bit of code:

sed 's/echo/echo\n/g' FILE | grep -c "echo"

This basically adds a newline following every instance of echo so they're each on their own line, allowing grep to count those lines. You can refine the regex if you only want the word "echo", as opposed to "echoing", for example.