2

So the idea is to replace matched pattern nas_... with nas_$SCL using $SCL variable in a file, but excluding 2 exact matches nas_mba && nas_tvr, which should not be replaced

So far I've got code excluding both matches, but also interfering with other unwanted matches

sed -i "s/nas_[^mt][^bv][^ar]/nas_$SCL/gI" filename.xml

How can I exclude only those 2 exact matches?

Update: So far I've found next solution

sed -i "/(nas_mba|nas_tvr)/! s/nas_.../nas_$SCL/"

but it skips a whole line if it has a match

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2 Answers 2

Reset to default
2

Here is how I would do it:

sed -E '/(nas_mba|nas_tvr)/! s/nas_.../nas_bar/'

Example:

echo "nas_mba
nas_tvr
nas_foo" | sed -E '/(nas_mba|nas_tvr)/! s/nas_.../nas_bar/'
nas_mba
nas_tvr
nas_bar

Only nas_foo in the original text is replaced, while both nas_mba and nas_tvr are left untouched.

Another example with more lines:

echo "nas_hat
> nas_mba
> nas_foo
> nas_hat
> nat_tvr
> nas_cat
> nas_dog" | sed -E '/(nas_mba|nas_tvr)/! s/nas_.../nas_bar/'
nas_bar
nas_mba
nas_bar
nas_bar
nat_tvr
nas_bar
nas_bar

If you want to change in place, just add the -i option (if you use GNU sed you don't need -i "" simply -i would suffice):

sed -E -i "" '/(nas_mba|nas_tvr)/! s/nas_.../nas_bar/' nas.txt 
cat nas.txt 
nas_bar
nas_mba
nas_bar
nas_bar
nat_tvr
nas_bar
nas_bar

Tested under Mac OS X 10.11.6 and BSD sed.

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4
  • yes, this is a good example, but this should be replace lines in a file, thus needing -i flag Commented Feb 3, 2017 at 8:15
  • 1
    Well, simply add the -i flag. See my edit. Commented Feb 3, 2017 at 8:18
  • cheers, works as intended Commented Feb 3, 2017 at 8:23
  • @MaxShepelev You're welcome! Commented Feb 3, 2017 at 8:24
2

If perl is an option, you could use lookahead:

export SCL
perl -pe 's/nas_(?!mba|tvr)\w*/nas_$ENV{SCL}/g' file

(note that this assumes the sequences you do want to match consist of word characters - it can be modified if that's not the case).

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