Teacher Foo and command line utilities

Newbie Unix came to teacher Foo and said: “I am in doubt. The Unix Great Path tells us that every program should focus on one thing and do it really well, right? ”

Teacher Foo nodded.

Rookie continued: “The Great Unix Path tells us that the bike doesn't need to be reinvented twice, right?”
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Teacher Foo nodded again.

“Then why are there several tools with similar word processing capabilities: sed , awk and Perl ? Which one of them will I better comprehend the Great Way of Unix? ”

Teacher Foo asked the newcomer: “What tool will you choose to create a copy of a text file with the replacement of several words?”

The newbie frowned and said, “ Perl ’s regular expressions would be like using a gun to shoot at sparrows. I don't know awk and write scripts on sed . Since I already have some experience using it, I would prefer it. But if this task of replacing text needs to be performed only once and there is no need to perform it constantly, then a text editor will be more than enough. ”

Teacher Foo nodded and said, “Eat when you are hungry. Drink when you are thirsty. Sleep when you're tired. ”

Upon hearing this, the novice attained enlightenment.