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The usual context of wildcard characters is in globbing similar names in a list of files, whereas regexes are usually employed in applications that pattern-match text strings in general. For example, the regex ^ [ \t] +| [ \t] +$ matches excess whitespace at the beginning or end of a line.
Perl, like sed before it, solves this problem by allowing many other characters to be delimiters for a regular expression. For example, the following three examples are equivalent to the expression given above: m{ftp://[^/]*/pub/} m#ftp://[^/]*/pub/# m!ftp://[^/]*/pub/! Or this common translation to convert backslashes to forward slashes:
A regular expression or regex is a sequence of characters that define a pattern to be searched for in a text. Each occurrence of the pattern may then be automatically replaced with another string, which may include parts of the identified pattern.
A screenshot of the original 1971 Unix reference page for glob – the owner is dmr, short for Dennis Ritchie.. glob() (/ ɡ l ɒ b /) is a libc function for globbing, which is the archetypal use of pattern matching against the names in a filesystem directory such that a name pattern is expanded into a list of names matching that pattern.
Regular Expression Flavor Comparison – Detailed comparison of the most popular regular expression flavors; Regexp Syntax Summary; Online Regular Expression Testing – with support for Java, JavaScript, .Net, PHP, Python and Ruby; Implementing Regular Expressions – series of articles by Russ Cox, author of RE2; Regular Expression Engines
find_character(string,char) returns integer Description Returns the position of the start of the first occurrence of the character char in string. If the character is not found most of these routines return an invalid index value – -1 where indexes are 0-based, 0 where they are 1-based – or some value to be interpreted as Boolean FALSE.
Python supports a wide variety of string operations. Strings in Python are immutable, so a string operation such as a substitution of characters, that in other programming languages might alter the string in place, returns a new string in Python. Performance considerations sometimes push for using special techniques in programs that modify ...
This number is called the edit distance between the string and the pattern. The usual primitive operations are: [1] insertion: cot → coat; deletion: coat → cot; substitution: coat → cost; These three operations may be generalized as forms of substitution by adding a NULL character (here symbolized by *) wherever a character has been ...