Question

Using egrep and grep in linux

1. Using sentences.txt
   1. Find all sentences that have words where there are two vowels in a row.
   2. Find all sentences that contain punctuation marks other than periods.
   3. Find all sentences that contain punctuation marks, including periods, that are not at the end of the sentence.
   4. Find all sentences that contain at least three words.
   5. Find all sentences that contain exactly four words.
   6. Find all sentences that contain words in which the letters (upper or lower case) a, b, c, and d appear in that order somewhere in the words (not necessarily consecutively). This should, for instance, find “a bat can die”.

What sentences.txt contains:

Anything goes here.

Or not

When, why or how.

A bat can die

The dog never does.

Yikes! he proclaimed

A big can of doo doo is gone.

The zebra never yells at x-rays well unless it is proscribed.

Once upon a time.

Farther. Back down the road!

Yes, a time once did exist

Answer 1

Hello there, hope you're having a good day. Let us start off with a brief of what grep and egrep are. grep is a command-line application or utility to check for patterns of text based on a specific regular expression in a specific line by line data. While egrep achieves the same purpose, it does so in a different way using certain characters as special meta characters.

For the specified questions:

1. grep -e "[aeiou][aeiou]" sentence.txt

The following command is broken down as:

-e specifies we are passing a regular expression

[aeiou][aeiou] marks the actual regular expression where the vowels would repeat.

2. grep -Ei '[[:punct:]]' sentence.txt | grep -Eiv [.]

Here, the Ei mode is used as i ignores case while E runs an extended regex. -v mode inverts matches which only returns unmatched lines. The built-in class [[:punct:]] contains all punctuations.

NB: for "." to be used in egrep, give escape character "\"

3.grep -E '[^[:punct:]]$' sentence.txt

Here, in extended regex mode, the [^] marks non existance of given characters where the characters are punctuations. The $ sign marks the end of the line.

4.grep -P '\w+\s+\w+\s+\w+' sentence.txt

Here, grep is launched in -P perl regex mode for easy searching of words and spaces wherein w+ is a word while s+ marks a spacing.

As the question contains 6 subparts but the student hasn't requested all parts to be answered, I am concluding my answers with that note.

I hope this helped you better understand grep. Thank you have a nice day.