computer_regular_expressions
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Regular Expressions
Explanation
Overview
PCRE2 Perl-compatible Regular Expressions
Tester
Syntax
PCRE1) pattern man page
man grep and info grep info pages for regular expression explanation and predefined named classes of characters like [:alnum:]
Check if PCRE2_UTF is set (echo $PCRE2_UTF) to check if ascii or UTF-8 syntax must be used. Source
| Code | Explanation |
|---|---|
| ? | Matches the previous token between zero and one times |
| {0,1} | Matches the previous token between zero and one times |
| * | Matches the previous token between zero and unlimited times |
| {0,} | Matches the previous token between zero and unlimited times |
| {32} | Matches the previous token exactly 32 times |
| + | Matches the previous token between one and unlimited times |
| {1,} | Matches the previous token between one and unlimited times |
| [0-9T:.+-] | Match a single character which may be: any digit, 'T' (case sensitive), ':', '.', '+' or a '-' |
| [[:something valid:]] | A character class. See man grep for valid entries like [:something valid:] |
| [._[:alnum:]-] | Match a single character which may be: '.', '_', '-', [:alnum:]. The '-' can not be placed at any position |
| A string | Matches an exact string. E.g. the sentence has to match |
| $ | Asserts position at the end of a line. Use when the end of the regex line coincides with the end of the line |
| '^$' | Matches an empty line, which consists of zero characters |
| (?# some text or a commented out rule) | Comment. A comment is inert, void, for the pattern matching behavior |
| # | Comment if unescaped and if the PCRE2_EXTENDED or PCRE2_EXTENDED_MORE option is set. 0x0a (the default newline) terminates the comment |
| 'left:[^;]*' | This regex matches the substring starting with left: and captures everything after it until the next semicolon (;). The [^;]* part matches any characters that are not a semicolon |
| \*\*[ ]* | Match ** followed by a undefined number of spaces |
Set PCRE2_EXTENDED
T.b.d.
Tools
check-regexp AAB$ "AAB DER GTY HUE AAB FERG GYT AAB"
Useful links
RegexBuddy
GNU.org on Regular Expressions
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Perl Compatible Regular Expressions
computer_regular_expressions.txt · Last modified: by wim