Re: Why TAB in ansi color is not recognized?

[Assaf Gordon]

Hello,

On 2019-04-28 11:23 a.m., Peng Yu wrote:
> In the 2nd example, it is not sorted as what I want. Why is it so?
>
> $ printf '%s\t%s\n' a 1 a 2 |grep --color=always a | sort -k 2,2nr
> a       2
> a       1
> $ printf '%s\t%s\n' a 1 a 2 | grep --color=always a$'\t' | sort -k 2,2nr
> a       1
> a       2

The 'grep' in the second example highlights *both* the 'a' character
and the 'tab' character.

This means that the ANSI sequence to restore color (\033 [ m \033  [ K)
appears *after* the tab, and is then parsed by 'sort' as the beginning
of the second field:

$ printf '%s\t%s\n' a 1 a 2 | grep --color=always a$'\t' | od -tc -An
 033   [   0   1   ;   3   1   m 033   [   K   a  \t 033   [   m
 033   [   K   1  \n 033   [   0   1   ;   3   1   m 033   [   K
   a  \t 033   [   m 033   [   K   2  \n

And annotated:

First line, first field:
   033   [   0   1   ;   3   1   m 033   [   K   a
   \t

First line, second field:
   033   [   m 033   [   K   1
   \n

Second line, first field:
   033   [   0   1   ;   3   1   m 033   [   K   a
   \t

Second line, second field:
   033   [   m 033   [   K   2
   \n


Using "--debug" will give a hint as to what went wrong:

  $ printf '%s\t%s\n' a 1 a 2 | grep --color=always a$'\t' \
       | sort -k2,2nr --debug
  sort: using ‘en_CA.utf8’ sorting rules
  a>1
           ^ no match for key
  ________________
  a>2
             ^ no match for key
  ________________


The "no match for key" message means that the 2nd field failed to be
parsed as a numeric value.



regards,
 -assaf