Abstract
The fourth grep problem from HackerRank.
grep a#
Problem#
An Introduction to Grep#
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 a 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.
More details about common examples of grep usage may be read here.
Before using grep it is recommended that one should become familiar with regular expressions, to be able to harness the command to its fullest.
Recommended References#
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.
Sample Input#
From fairest creatures we desire increase, That thereby beauty’s rose might never die, But as the riper should by time decease, His tender heir might bear his memory: But thou contracted to thine own bright eyes, Feed’st thy light’s flame with self-substantial fuel, Making a famine where abundance lies, Thy self thy foe, to thy sweet self too cruel: Thou that art now the world’s fresh ornament, And only herald to the gaudy spring, Within thine own bud buriest thy content, And tender churl mak’st waste in niggarding: Pity the world, or else this glutton be, To eat the world’s due, by the grave and thee. When forty winters shall besiege thy brow, And dig deep trenches in thy beauty’s field, Thy youth’s proud livery so gazed on now, Will be a tattered weed of small worth held: Then being asked, where all thy beauty lies, Where all the treasure of thy lusty days; To say within thine own deep sunken eyes, Were an all-eating shame, and thriftless praise. How much more praise deserved thy beauty’s use, If thou couldst answer ‘This fair child of mine Shall sum my count, and make my old excuse’
Sample Output#
That thereby beauty’s rose might never die, But as the riper should by time decease, Thou that art now the world’s fresh ornament, And only herald to the gaudy spring, Pity the world, or else this glutton be, To eat the world’s due, by the grave and thee. Then being asked, where all thy beauty lies, Where all the treasure of thy lusty days;
Explanation#
We retain only those lines which have at least one of the following words:
the that then those