Regular expressions 8. Substitution special characters
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The substitution string is mostly interpreted as ordinary text except for the special control characters, the octal and hexadecimal escapes and the following character combinations:
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\1 ... \9 are backreferences at sub-expressions 1 ... 9 in the match.
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Any of the first nine sub-expressions of the match string can be inserted into the replacement string by inserting a “\” followed by a digit from 1 to 9 that represents the string matched by a parenthesized expression within the regular expression. The numbering is left to right.
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Example: A search for "(a)(b)" in the string "abc", followed by a replace "\2\1" results in "bac".
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& reference at entire match.
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The entire string that was matched by the search operation will be substituted.
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Example: a search for "." in the string "abcd" followed by the replace "&&" doubles every character in the result "aabbccdd".
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\U \u to uppercase.
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The text inserted by "&" or "\1" ... "\9" is converted to uppercase ("\u" only changes the first character to uppercase).
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Example: A search for "(aa)" in the string "aabb", followed by a replace "\U\1bc" results in the string "AAbcbb".
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\L \l to lowercase.
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The text inserted by "&" or "\1" ... "\9" is converted to lowercase ("\l" only changes the first character to lowercase).
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Example: A search for "(AA)" with a replace "\l\1bc" in the string "AAbb" results in the string "aAbcbb".
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