QUESTION 4 PLEASE 1. What is the difference between ~grep~ and ~egrep~? What add
ID: 3745353 • Letter: Q
Question
QUESTION 4 PLEASE
1. What is the difference between ~grep~ and ~egrep~? What additional symbols are added?
The only difference is the way they interpret the pattern. grep stands for Global Regular Expressions Print.
egrep stands for Extended Global Regular Expressions Print.+ ? | are the additional symbols
2. Give an example of something that is easy to match but hard to validate (but not an example used in the lecture).
3. Is this a valid regular expression pattern, ~[a-zA-Z0-9]~? If so, what does it match?
4. Write *two* ~egrep~ commands to look for occurances of "abc" in a file called ~letters.txt~.
5. Modify one of the previous commands to just print how many occurances occured. Use the ~wc~ command to
count how many lines there were.
6. What are the two replacement strings for regex? Give an example of both of them.
Explanation / Answer
4. Write *two* ~egrep~ commands to look for occurances of "abc" in a file called ~letters.txt~.
Search for various combinations of abc in letters.txt
egrep 'abc|ABC|aBC|abC|ABc' letters.txt
Search for case insensitivite abc in letters.txt
egrep -i abc letters.txt
Please let me know in case of any clarifications required. Thanks!