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Tweak markdown to properly render html

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carl
2019-09-20 14:12:41 +10:00
parent aa7020998b
commit edcfd31759
3 changed files with 31 additions and 16 deletions
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pcre.html.markdown
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@@ -3,16 +3,18 @@ language: PCRE
filename: pcre.txt
contributors:
- ["Sachin Divekar", "http://github.com/ssd532"]
---
A regular expression (regex or regexp for short) is a special text string for describing a search pattern. e.g. to extract domain name from a string we can say `/^[a-z]+:/` and it will match `http:` from `http://github.com/`.
A regular expression (regex or regexp for short) is a special text string for describing a search pattern. e.g. to extract domain name from a string we can say `/^[a-z]+:/` and it will match `http:` from `http://github.com/`.
PCRE (Perl Compatible Regular Expressions) is a C library implementing regex. It was written in 1997 when Perl was the de-facto choice for complex text processing tasks. The syntax for patterns used in PCRE closely resembles Perl. PCRE syntax is being used in many big projects including PHP, Apache, R to name a few.
There are two different sets of metacharacters:
* Those that are recognized anywhere in the pattern except within square brackets
```
\ general escape character with several uses
^ assert start of string (or line, in multiline mode)
@@ -32,18 +34,19 @@ There are two different sets of metacharacters:
```
* Those that are recognized within square brackets. Outside square brackets. They are also called as character classes.
```
\ general escape character
^ negate the class, but only if the first character
- indicates character range
[ POSIX character class (only if followed by POSIX syntax)
] terminates the character class
```
PCRE provides some generic character types, also called as character classes.
```
PCRE provides some generic character types, also called as character classes.
```
\d any decimal digit
\D any character that is not a decimal digit
@@ -59,7 +62,13 @@ PCRE provides some generic character types, also called as character classes.
## Examples
We will test our examples on following string `66.249.64.13 - - [18/Sep/2004:11:07:48 +1000] "GET /robots.txt HTTP/1.0" 200 468 "-" "Googlebot/2.1"`. It is a standard Apache access log.
We will test our examples on the following string:
```
66.249.64.13 - - [18/Sep/2004:11:07:48 +1000] "GET /robots.txt HTTP/1.0" 200 468 "-" "Googlebot/2.1"
```
It is a standard Apache access log.
| Regex | Result | Comment |
| :---- | :-------------- | :------ |