Re: Indexing Unix command

[Christian Seiler <christian@iwakd.de>]

On 08/01/2016 02:52 PM, Rodolfo Medina wrote:
> with the following simple script:
> 
> #!/bin/sh
> 
> cat index.idx | sort > index.ind
> 
> I sort the contents of a file and write it in another file.  Now, I want that a
> small vertical space, i.e. an empty line or two, were inserted before all the
> words that start with a new letter.

If the first letters of your words are only ASCII characters
(or you are using an 8 bit character encoding), then the
following should do the trick:

sort < index.idx | awk 'BEGIN {
          c = -1;
        }
        {
          if (substr($0, 1, 1) != c && c != -1)
            printf("\n\n");
          c = substr($0, 1, 1);
          print;
        }' > index.ind

See also:
https://en.wikibooks.org/wiki/AWK

Regards,
Christian