regular expressions Definition

Regular expressions are combinations of special character operators, which are symbols that control the search, that you can use to construct search strings for advanced find and/or replace searches.

The regular expressions used to perform searches in the Quartus^® Prime software are the same as those used in many Linux applications. For more information about regular expressions, see Jeffrey E.F. Friedl's Mastering Regular Expressions (Sebastopol: O'Reilly & Associates, Inc., 1997).

The table below shows examples of regular expression metacharacters, their descriptions, and their applications:

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Operator	Description	Example
`.` (dot)	Matches any single character of the input line.	`.op` finds top and hop, and it also finds the substring, top, in stop.
`^`	This metacharacter does not match any character but represents the beginning of the input line.	`^A` finds the letter A at the beginning of a line.
`?`	Matches a string of zero or one character that would match the character to the immediate left of ?.	`m?y` finds the substring y in the words, by and gray, and it also finds the entire word, my.
`$`	This metacharacter does not match any character but represents the end of an input line.	`end$` finds end when it is the last string on a line.
\	This metacharacter is used to turn off the special meaning of metacharacters.	`\.` finds only the . (dot) character. `\?` finds only the ? character.
`[...]`	Matches one or more characters or a range of characters in the set.	`[a-c]at` finds bat and cat, but not sat.
`[^...]`	Matches one or more characters or a range of characters not in the set.	`[^a-c]at` finds sat and rat, but not bat or cat.
`+`	Matches a string of one or more characters that would match the character to the immediate left of `+`.	`m+e` finds me, but not made, mine, or more.
`*`	Matches a string of zero or more characters that would match the character to the immediate left of *.	`m*y` finds the substring y in the words, by and gray, and it also finds the entire word, my, as well as the substring, mmy, in the word, mummy.

The table below shows how to construct a regular expression search for special characters:

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To find:	Use the regular expression:
newline characters	`\n`
tabs	`\t`
.(dot), *, ?, ^, and other metacharacters used in regular expression searches	`\.`, `\*`, `\?`, `\^`, and so on.