How to toggle cases with sed command?

Question

I want to replace kAbcdedf with abcdef in a file. I try to use the sed command. Some suggestions said, if I input this command

echo 'abc'|sed 's/^../\u&/'

the result will be

Abc

but on macOS (using zsh), the result is

uabc

Does anyone know the correct way to toggle cases with the sed command?

How can I search kAbcd and then replace that string with abcd, i.e., remove k and uppercase the next letter after k?

can you please change the tag from linux to mac? as far as I know, the sed on mac(not sure what it is called exactly) doesn't support `\u` — Sundeep, May 08 '18 at 12:15
You need GNU sed to use that feature. See [How to use GNU sed on Mac OS X](https://stackoverflow.com/questions/30003570/how-to-use-gnu-sed-on-mac-os-x) — Wiktor Stribiżew, May 08 '18 at 12:16
also, based on example given, you want to lowercase the character after `k`, not uppercase — Sundeep, May 08 '18 at 12:17

score 2 · Answer 1 · answered May 08 '18 at 12:22

2

$ # with GNU sed
$ echo 'kAbcd' | sed -E 's/k(.)/\l\1/'
abcd

$ # with perl if GNU sed is not available
$ echo 'kAbcd' | perl -pe 's/k(.)/\l$1/'
abcd

As mentioned by Wiktor Stribiżew in comments, see also: How to use GNU sed on Mac OS X

answered May 08 '18 at 12:22

Sundeep

By the way, if I want with GNU sed to covert abcd.kAbcd to abcd.abcd, how should I write command? thanks~ – whitekevin May 09 '18 at 07:03
the same command as mentioned in the answer.. by default, matching is done anywhere in the line.. you can change that using anchors, word boundaries and other things.. see https://www.gnu.org/software/sed/manual/sed.html#sed-regular-expressions for details – Sundeep May 09 '18 at 07:51

1 Answers1