Multiply found text in sed - is it possible?

xerostomus

8/27/24, 1:10 PM

This is what I have:

echo -e "a\t4\nb\t7\nc\t2\nd\t12\n" | sed -rn 's/(.*)\t([0-9]*)$/\2\t\1\1\1\t/p'

4   aaa  
7   bbb 
2   ccc 
12  ddd

This I want:

4   aaaa    
7   bbbbbbb  
2   cc  
12  dddddddddddd

Is this possible in sed only or I have to use some other tools?

134

1 + 3

command-line

sed

text-processing

steeldriver

8/27/24, 1:31 PM

It would certainly be *simpler* in other tools - perl for example has a string repetition operator ex. `printf '%c\t%d\n' a 4 b 7 c 2 d 12 | perl -F'\t' -lne 'print join "\t", $F[1], $F[0] x $F[1]'`

Raffa

8/27/24, 6:46 PM

I would go with @steeldriver perl script for sure.

xerostomus

8/28/24, 5:13 PM

You are right -- points up for Perl. :-) Thanks.

Score:3

Ubuntu

Raffa

8/27/24, 6:42 PM

Not really totally pure sed, but rather with setting the flag e which allows for embedding shell commands and executing them and allows for risky command injection as well so know that one and do (if you have to) on your own risk.

Not really my preferred way either but you asked for it.

That said, you can do it with something like this:

$ echo -ne "a\t4\nb\t7\nc\t2\nd\t12\n" |
sed -rn "s/(.*)\t([0-9]*)$/bash -c \"printf '%s\t' \2; printf '\1%.0s' {1..\2}\"/ep"
4   aaaa
7   bbbbbbb
2   cc
12  dddddddddddd

+ 3

steeldriver

8/27/24, 8:40 PM

You could avoid the extra (bash) shell by using `seq` in place of the brace expansion in the replacement: `printf '%s\t' \2; printf '\1%.0s' \$(seq \2)`

Raffa

8/28/24, 6:21 AM

Yes, @steeldriver that would offer more portability … Although, starting an extra shell/sub-shell seems unavoidable both ways.

xerostomus

8/28/24, 5:29 PM

Raffa, I can do it to in Python or Bash, but I thought sed could be more elegant way. You are right that Perl is most elegant by now, but I do not know it much. I guess that awk could also do the job. I prefer to know less programming languages deeper then to know many languages superficially. So thank you all for nice jobs. :-)

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