HackerRank Grep – A problem solution

In this HackerRank Grep – A problem-solution Grep is a multi-purpose search tool, which is used to find specified strings or regular expressions. A variety of options exist, which make it possible to use the command in several different ways and to handle many different situations. For example, one might opt for case-insensitive search, or to display only the fragment matching the specified search pattern, or to display only the line number of an input file where the specified string or regular expression has been found.

Before using grep it is recommended that one should become familiar with regular expressions, to be able to harness the command to its fullest.

Current Task

Given a text file, which will be piped to your command through STDIN, use grep to display all those lines which contain any of the following words in them:

the

that

then

those

The search should not be sensitive to case. Display only those lines of an input file, which contain the required words.

Input Format

A text file with multiple lines will be piped to your command through STDIN.

Output Format

Display the required lines without any changes to their relative ordering.

Problem solution.

grep -i -e "the " -e"that " -e "then " -e "those "

Second solution.

grep  -iwe "the" -we "that" -we "then" -we "those"

Third solution.

grep -iw 'the|that|then|those'

Fourth solution.

grep -iwE 'th(e|at|en|ose)'