Start of a string.
The caret is used to "anchor" the search to the start of the string. If the search is not anchored to either end, the pattern can match a sub-string of the target.
For example:
^abc matches abc, abcdefg, abc123, but not 123abc
abc also matches// 123abc//
End of a string.
The dollar sign is used to "anchor" the search to the end of the string. If the search is not anchored to either end, the pattern can match a sub-string of the target.
For example:
abc$ matches abc, endsinabc, 123abc, but not abc123
^abc(.\*)123$ matches abc123, abcxyz123, but not abcxyz123def
Any single character.
The period (full stop) is used to match any single character.
For example:
a.c matches abc, aac, acc, adc but not acd
0 or more of previous expression.
Matches zero or more occurrences of the previous expression. Combine with . to form the "match anything" token (.*).
For example:
ab*c matches ac, abc, abbc, abbbc, ...
a.*c matches ac, abc, a123456c, aanythingc, ...
.* matches anything
1 or more of previous expression.
Matches one or more occurrences of the previous expression.
For example:
ab+c matches abc, abbc, abbbc but not ac
0 or 1 of previous expression.
Matches either zero or one occurrence of the previous expression.
For example:
ab?c matches ac, abc but not abbc or abbbc
Alternation (logical or).
The vertical bar is used to separate two or more characters or expressions, any of which may match.
For example:
a | b matches a or b
a(b | c)d matches abd or acd
(bill | ted) matches bill or ted
Quantifier.
Braces are used to indicate that the preceding expression must match an exact number of times.
For example:
ab{2}c matches abbc, but not abc or abbbc
a.{4}z matches abcdez, a1234z, afourz, aaaaaz, etc.
Character set.
Matches any single character in the set of specified characters.
You can specify the character set as individual characters (e.g. \[abdfg]) or as a range of characters (e.g. \[a-j]) or as multiple ranges.
For example:
\[abc] matches either a, b or c
\[af-j] matches either a, f, g, h or j
\[a-dh-kq-] matches a, b, c, d, h, i, j, k, or any character from q onwards
IMGP\[0-9]{4}.jpg matches IMGP0158.jpg (or any other four-digit number).
Negative character set.
Matches any character not in the set of specified characters. See \[] for information on how the set is defined.
For example:
\[^pqr] matches any character except p, q or r
Expression / capture group.
Parentheses are used to combine multiple characters into an expression. When used in a "search and replace" like Advanced Rename, they also mark capture groups - see above for a discussion of these.
For example:
a | bc matches ac or bc, whereas
a | (bc) matches a or bc
Escape character.
The backslash is used to escape token characters in order to match those characters literally.
When used before a non-token character, it is used to indicate the following special escape characters:
\
\\
It is also used to mark several character classes, which are shorthand ways to specify various common \[] character sets (see below).
For example:
a | b matches a or b, whereas
a\b matches a | b\ a matches a followed by a tab character, whereas
a matches a
Word character.
Matches any word character. Equivalent to \[a-zA-Z\_0-9].
For example:
^\w+\[0-9]{4}.jpg matches IMGP0158.jpg (or any other four-digit number preceded by at least one other word character).
Non-word character.
Matches any non-word character, equivalent to \[^a-zA-Z\_0-9].
Space character.
Matches any whitespace character. Equivalent to \[ \f\n\r\t\v].
Non-space character.
Matches any non-whitespace character. Equivalent to \[^ \f\n\r\t\v].
Digit character.
Matches any decimal digit. Equivalent to \[0-9].
Non-digit character.
Matches any non-decimal digit. Equivalent to \[^0-9].
For example:
^\D+\d{4}.jpg matches IMGP0158.jpg (or any other four-digit number preceded by at least one non-digit character).