Question

Write an egrep command that prints out all the valid ID numbers in the file lines.txt. A valid ID number has the following rules:

• It starts with a hash mark (#) followed by 3 digits, one dash (-) and another group of 5 digits.
• There is an optional letter in front (before the hash mark) that can be from A to F (including A and F).

NOTE: Look at the lines.txt file for examples of valid and invalid ID numbers. Also, you can assume all ID numbers start at the beginning of the line and end with a space (this is useful as egrep will pick up strings within the invalid ID's that are valid).

Answer 1

The command will be as follows

egrep -c '^#[0-9][0-9][0-9]-[0-9][0-9][0-9][0-9][0-9] | ^[A-F]#[0-9][0-9][0-9]-[0-9][0-9][0-9][0-9][0-9]' line.txt

starts with a hash mark (#) followed by 3 digits from 0-9) , one dash (-) and another group of 5 digits from 0-9

[0-9]--> Any number from 0-9

[A-F]--> Any alphabet between A and F includeind both letters

The above command will serach for all IDs starts with a hash mark (#) followed by 3 digits from 0-9) , one dash (-) and another group of 5 digits from 0-9 OR starts with OPTIONAL LETTER [A-Z]hash mark (#) followed by 3 digits from 0-9) , one dash (-) and another group of 5 digits from 0-9

Please note line.txt is not available in the question for sample check