What is the output when the regular expression s/[ABC] [abc]/xx/ is applied to the following string?

8 thoughts on “What is the output when the regular expression s/[ABC] [abc]/xx/ is applied to the following string?”

1. echo “ABCabc” | sed ‘s/[ABC] [abc]/xx/’
   ABCabc
   Ans: D

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2. echo ABCabc |sed s/[ABC][abc]/xx/ -> ABxxbc

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3. [ABC][abc] = Aa Ab Ac Ba Bb Bc Ca Cb Cc
   only Ca is a part of the string “ABCabc”
   The correct Answer is A

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4. The answer is A.
   Only at the part Ca matches the argument and perform substitution.

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   1. if in s/[ABC] [abc]/xx/ there is a space, the answer is D, if there is no space between [ABC] [abc] the answer is A.

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      1. If there is a space between [ABC] [abc], an error message is displayed.

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         1. echo ABCabc | sed ‘s/[ABC] [abc]/xx/’
            ABCabc

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      2. correct. But what is the logic in it ?

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