Tcl Built- In Commands - re_syntax manual page. NAMEre_syntax - Syntax of Tcl regular expressions. DESCRIPTIONDIFFERENT FLAVORS OF REs. REGULAR EXPRESSION SYNTAX*+?{m}{m,}{m,n}*? BRACKET EXPRESSIONSESCAPES\a\b\B\c. X\e\f\n\r\t\uwxyz\Ustuvwxyz\v\xhhh\0\xy\xyz\d\s\w\D\S\W\A\m\M\y\Y\Z\m\mnn. METASYNTAXbceimnpqstwx.
MATCHINGLIMITS AND COMPATIBILITYBASIC REGULAR EXPRESSIONSSEE ALSOKEYWORDS. Syntax of Tcl regular expressions.
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A regular expression describes strings of characters. It's a pattern that matches certain strings and doesn't match others. Regular expressions (``RE''s), as defined by POSIX, come in two. REs (``EREs'') and basic REs (``BREs''). EREs are roughly those of the traditional egrep, while BREs are. This implementation adds.
REs (``AREs''), basically EREs with. This manual page primarily describes AREs. BREs mostly exist for. POSIX EREs are almost an exact subset of AREs. Features of. AREs that are not present in EREs will be indicated.
Tcl regular expressions are implemented using the package written by. Henry Spencer, based on the 1.
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Perl. 5 extensions (thanks, Henry!). Much of the description of.
1.3 Getting Started : Atom Basics Atom Basics. Now that Atom is installed on your system, let’s fire it up, configure it and get acquainted with the editor.
An ARE is one or more branches. A branch is zero or more constraints or quantified atoms. It matches a match for the first, followed by a match for the second, etc. A quantified atom is an atom possibly followed. Without a quantifier, it matches a match for the atom. The quantifiers. and what a so- quantified atom matches, are.
MATCHING). The forms using. An atom is one of. BRACKET EXPRESSIONS for more detail).
Intel® 64 and IA-32 Architectures Software Developer’s Manual Volume 1: Basic Architecture NOTE: The Intel® 64 and IA-32 Architectures Software Developer's. Basic Micro Studio Syntax Manual. Warranty. As with most BASIC implementations, Atom BASIC includes a full complement of math and comparison functions. The syntax of textual programming languages is usually defined using a combination of regular expressions (for lexical structure) and Backus–Naur Form (for.
AREs only). see ESCAPES below. A constraint matches an empty string when specific conditions. A constraint may not be followed by a quantifier.
User manual & syntax. Release notes. FAQ. This page contains all possible syntax you may use when. Creates a gallery of images from a namespace or RSS/ATOM feed.
The simple constraints are as follows; some more constraints are. ESCAPES. matches at the beginning of a line. AREs only), matches at any point. AREs only), matches at any point. The lookahead constraints may not contain back references (see later). An RE may not end with `\'.
A bracket expression is a list of characters enclosed in `[ ]'. It normally matches any single character from the list (but see below). If the list begins with `^'. If two characters in the list are separated by `- '.
ASCII matches any decimal digit. Two ranges may not share an. Ranges are very collating- sequence- dependent. To include a literal. AREs only) precede it with `\'. Alternatively, for `- '. To use a literal.
AREs only) precede it with `\'. With the exception of these, some combinations using. Within a bracket expression, a collating element (a character. The sequence is a single element of the bracket expression's list. A bracket expression in a locale that has.
So (insidiously), a bracket expression that starts with ^. Note: Tcl currently has no multi- character collating elements. This information is only for illustration.). For example, assume the collating sequence includes a ch.
Then the RE [[. ch.]]*c (zero or more ch's followed by c). Also, the RE [^c]b matches all of `chb'. Within a bracket expression, a collating element enclosed in. If there are no other equivalent collating elements. For example, if. are the members of an equivalence class. An equivalence class may not be an endpoint.
Tcl currently implements only the Unicode locale. It doesn't define any equivalence classes. The examples above are just illustrations.). Within a bracket expression, the name of a character class enclosed. Standard character classes are. A letter. upper An upper- case letter. A lower- case letter.
A decimal digit. xdigit A hexadecimal digit. An alphanumeric (letter or digit). A "printable" (same as graph, except also including space). A space or tab character. A character producing white space in displayed text. A punctuation character. A character with a visible representation.
A control character. A locale may provide others. Note that the current Tcl implementation has only one locale. Unicode locale.). A character class may not be used as an endpoint of a range.
There are two special cases of bracket expressions. A word is defined as a sequence of. A word character is an.
These special bracket expressions are deprecated. AREs should use constraint escapes instead (see below). Escapes (AREs only), which begin with a. AREs. In EREs, there are no escapes. The latter is the one actual incompatibility between EREs and AREs.). Character- entry escapes (AREs only) exist to make it easier to specify. REs. alert (bell) character, as in C.
C. to help reduce backslash doubling in some. X is any character) the character whose.
C. newline, as in C. C. horizontal tab, as in C. Unicode character. Unicode extension to 3.
C. are all available. Hexadecimal digits are `0'- `9', `a'- `f'. Octal digits are `0'- `7'. The character- entry escapes are always taken as ordinary characters. Beware, however, that some applications (e.
C compilers) interpret. Class- shorthand escapes (AREs only) provide shorthands for certain commonly- used. Within bracket expressions, `\d', `\s'. D', `\S'. (So, for example, [a- c\d] is equivalent to [a- c[: digit: ]]. Also, [a- c\D], which is equivalent to [a- c^[: digit: ]], is illegal.).
A constraint escape (AREs only) is a constraint. MATCHING, below, for how this differs from `^'). MATCHING, below, for how this differs from `$').
A word is defined as in the specification of. Constraint escapes are illegal within bracket expressions. A back reference (AREs only) matches the same string matched by the parenthesized. The subexpression must entirely precede the back reference in the RE.
Subexpressions are numbered in the order of their leading parentheses. Non- capturing parentheses do not define subexpressions. There is an inherent historical ambiguity between octal character- entry. A leading zero always indicates an octal escape. A single non- zero digit, not followed by another digit. A multi- digit sequence not starting with a zero is taken as a back.
In addition to the main syntax described above, there are some special. Normally the flavor of RE being used is specified by. However, this can be overridden by a director. If an RE of any flavor begins with `***: '. RE is an ARE. If an RE of any flavor begins with `***='.
RE is taken to be a literal string. An ARE may begin with embedded options.
RE. These supplement, and can override. The available option letters are. RE is a BRE. case- sensitive matching (usual default).
RE is an ERE. case- insensitive matching (see MATCHING, below). MATCHING, below).
MATCHING, below). RE is a literal (``quoted'') string, all ordinary characters.
MATCHING, below). Embedded options take effect at the.
They are available only at the start of an ARE. In addition to the usual (tight) RE syntax, in which all characters are. RE. with the - expanded switch, or in AREs with the embedded x option.
In the expanded syntax. RE) are ignored. permitting paragraphing and commenting a complex RE. There are three exceptions to that basic rule. ARE `(?: ' or the BRE `\('.
Expanded- syntax white- space characters are blank, tab, newline, and. Finally, in an ARE. Again, this is not allowed between the characters of. Such comments are more a historical artifact than a useful facility. None of these metasyntax extensions is available if the application. RE. In the event that an RE could match more than one substring of a given. RE matches the one starting earliest in the string.
If the RE could match more than one substring starting at that point. Most atoms, and all constraints, have no preference. A parenthesized RE has the same preference (possibly none) as the RE. A quantified atom with quantifier. A quantified atom with other normal quantifiers (including.
A quantified atom with other non- greedy quantifiers (including. A branch has the same preference as the first quantified atom in it.
An RE consisting of two or more branches connected by the. Subject to the constraints imposed by the rules for matching the whole RE.
RE taking priority over. Note that outer subexpressions thus take priority over.
Note that the quantifiers. RE. Match lengths are measured in characters, not collating elements. An empty string is considered longer than no match at all. RE and the parenthesized.
If case- independent matching is specified. When an alphabetic that exists in multiple cases appears as an.
X]'. When it appears inside a bracket expression, all case counterparts. X]'. If newline- sensitive matching is specified, . RE. explicitly arranges it). If partial newline- sensitive matching is specified. If inverse partial newline- sensitive matching is specified. This isn't very useful but is provided for symmetry.
No particular limit is imposed on the length of REs. Programs intended to be highly portable should not employ REs longer. POSIX- compliant implementation can refuse to accept such REs. The only feature of AREs that is actually incompatible with.
POSIX EREs is that. All other ARE features use syntax which is illegal or has. POSIX EREs. syntax of directors likewise is outside the POSIX. BREs and EREs. Many of the ARE extensions are borrowed from Perl, but some have. Perl extensions are not present. Incompatibilities of note include `\b', `\B'.
The matching rules for REs containing both normal and non- greedy quantifiers. The new rules are much simpler and cleaner. Henry Spencer's original 1. Tcl). implemented an early version of today's EREs.
There are four incompatibilities between regexp's near- EREs. RREs' for short) and AREs. In roughly increasing order of significance. RREs, it was just another way of writing the. This should not be a problem because there was no reason to write. RREs. followed by a digit in an ARE is the beginning of a bound. Such sequences should be rare.
AREs report the longest/shortest match for the RE. This may affect some RREs which were written in the expectation that. The careful crafting of RREs to optimize the search order for fast. AREs examine all possible matches. BREs differ from EREs in several respects. The delimiters for bounds are.
The parentheses for nested subexpressions are. RE or the beginning of a parenthesized subexpression. RE or the end of a parenthesized subexpression.