Re: sed "Hello, world!" program?

On 2014-02-18 13:09, [email protected] wrote:
> Most programming languages have a "Hello, world!" example. Some
> might debate if sed is a "real" programming language. But sed at
> least resembles a programming language in many ways. Anyway,
> assuming sed is a programming language, what might be sed "Hello,
> world!" program?

Well, you can pull of a UUOC¹ using sed as a noop

  echo 'Hello, World!' | sed '$q'

or you can transform input into your desired string:

  echo | sed 's/.*/Hello, world!/;q'

or you can transform every input line into your desired string

  echo | sed 's/.*/Hello, world!/'

> I think the criteria are:
>  Prints "Hello, world!".
>  Is one of the simplest programs in the language
>  Can be useful to demonstrate the language.

I think the 3rd one is the closest to meeting those criteria.

> Perhaps this is a silly post. Or maybe it might interest someone,
> or make us think more about how sed works. 

Since sed is more often used as a filter than as a stand-alone
language, it feels a little awkward to coerce it into acting like a
stand-alone language.  That said, it doesn't stop people from doing
crazy things with sed like Tetris², Conway's game of life³, or a
Sudoku solver⁴.

-tkc


¹ http://www.catb.org/jargon/html/U/UUOC.html
² http://uuner.doslash.org/forfun/
³ http://permalink.gmane.org/gmane.editors.sed.user/3770
⁴ http://www.edwardrosten.com/code/sed/sedoku.sed