Home/ Questions/Q 8041911
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-06-05T04:23:20+00:00

Using sed, how to change the letter ‘a’ to ‘A’ but only if it

  • 0

Using sed, how to change the letter ‘a’ to ‘A’ but only if it appears repeated as two or more consecutive letters. Example, from:

galaxy
ear
aardvak
Haaaaaaaaa

into

galaxy
ear
AArdvak
HAAAAAAAAA
Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    You can do it using groups. If you have this file:

    $ cat a
galaxy
ear
aardvak
Haaaaaaaaa 
Ulaanbaatar

    You can use this sed command:

    $ sed 's/\(.\)\1\{1,\}/\U&/g' a
galaxy
ear
AArdvak
HAAAAAAAAA 
UlAAnbAAtar

    What does happen here? If we have a char, “packed” in a group (\(.\)), and this group (\1) repeats itself one or more times (\1\{1,\}), then replace the matched part (&) by its uppercased version (\U&).

    • 0