Here is my cheatsheet that has been very helpful. Obviously, this will not teach you how RegEx works, but is a good quick reference when I forget the exact syntax for something.
RegExp
Character classes
Pattern
Description
.
Any character, except newline
\w
Word
\d
Digit
\s
Whitespace
\W
Not word
\D
Not digit
\S
Not whitespace
[abc]
Any of a, b, or c
[a-e]
Characters between a and e
[1-9]
Digit between 1 and 9
[[:print:]]
Any printable character including spaces
[^abc]
Any character except a, b or c
Anchors
Pattern
Description
\G
Start of match
^
Start of string *
$
End of string *
\A
Start of string
\Z
End of string
\z
Absolute end of string
\b
A word boundary
\B
Non-word boundary
^abc
Start with abc
abc$
End with abc
For multiline patterns (m flag), ^ and $ will act as start and end of line.
Escaped characters
Pattern
Description
\. \* \\
Escape special character used by regex
\t
Tab
\n
Newline
\r
Carriage return
Groups
Pattern
Description
(abc)
Capture group
(a|b)
Match a or b
(?:abc)
Match abc, but don’t capture
\1
Substituted with text matched of the 1st capturing group
Quantifiers
Pattern
Description
a*
Match 0 or more
a+
Match 1 or more
a?
Match 0 or 1
a{5}
Match exactly 5
a{,3}
Match up to 3
a{3,}
Match 3 or more
a{1,3}
Match between 1 and 3
Lookahead & Lookbehind
Pattern
Description
a(?=b)
Match a in baby but not in bay
a(?!b)
Match a in Stan but not in Stab
(?<=a)b
Match b in crabs but not in cribs
(?<!a)b
Match b in fib but not in fab
(?<![a-z])abc(?![a-z])
Match abc without any letters before/after
Raw Markdown
# RegExp## Character classes
| Pattern | Description |
| ------------- | ---------------------------------------- |
| `.` | Any character, except newline |
| `\w` | Word |
| `\d` | Digit |
| `\s` | Whitespace |
| `\W` | Not word |
| `\D` | Not digit |
| `\S` | Not whitespace |
| `[abc]` | Any of a, b, or c |
| `[a-e]` | Characters between `a` and `e` |
| `[1-9]` | Digit between `1` and `9` |
| `[[:print:]]` | Any printable character including spaces |
| `[^abc]` | Any character except `a`, `b` or `c` |
## Anchors
| Pattern | Description |
| ------- | ---------------------- |
| `\G` | Start of match |
| `^` | Start of string \* |
| `$` | End of string \* |
| `\A` | Start of string |
| `\Z` | End of string |
| `\z` | Absolute end of string |
| `\b` | A word boundary |
| `\B` | Non-word boundary |
| `^abc` | Start with `abc` |
| `abc$` | End with `abc` |
For multiline patterns (`m` flag), `^` and `$` will act as start and end of line.
## Escaped characters
| Pattern | Description |
| ---------- | -------------------------------------- |
| `\. \* \\` | Escape special character used by regex |
| `\t` | Tab |
| `\n` | Newline |
| `\r` | Carriage return |
## Groups
| Pattern | Description |
| --------- | -------------------------------------------------------- |
| `(abc)` | Capture group |
| `(a\|b)` | Match `a` or `b` |
| `(?:abc)` | Match `abc`, but don't capture |
| `\1` | Substituted with text matched of the 1st capturing group |
## Quantifiers
| Pattern | Description |
| -------- | --------------------- |
| `a*` | Match 0 or more |
| `a+` | Match 1 or more |
| `a?` | Match 0 or 1 |
| `a{5}` | Match exactly 5 |
| `a{,3}` | Match up to 3 |
| `a{3,}` | Match 3 or more |
| `a{1,3}` | Match between 1 and 3 |
## Lookahead & Lookbehind
| Pattern | Description |
| --- | --- |
| `a(?=b)` | Match `a` in `baby` but not in `bay` |
| `a(?!b)` | Match `a` in `Stan` but not in `Stab` |
| `(?<=a)b` | Match `b` in `crabs` but not in `cribs` |
| `(?<!a)b` | Match `b` in `fib` but not in `fab` |
| `(?<![a-z])abc(?![a-z])` | Match `abc` without any letters before/after |
How so? I have been getting much more comfortable with it lately, but I am curious what downsides there are
The downsides are having to relearn it every time you need to understand it.
Just use something like https://regex101.com/
not really i just meant they suck to remember how to write without looking up :)
Here is my cheatsheet that has been very helpful. Obviously, this will not teach you how RegEx works, but is a good quick reference when I forget the exact syntax for something.
RegExp
Character classes
.\w\d\s\W\D\S[abc][a-e]aande[1-9]1and9[[:print:]][^abc]a,borcAnchors
\G^$\A\Z\z\b\B^abcabcabc$abcFor multiline patterns (
mflag),^and$will act as start and end of line.Escaped characters
\. \* \\\t\n\rGroups
(abc)(a|b)aorb(?:abc)abc, but don’t capture\1Quantifiers
a*a+a?a{5}a{,3}a{3,}a{1,3}Lookahead & Lookbehind
a(?=b)ainbabybut not inbaya(?!b)ainStanbut not inStab(?<=a)bbincrabsbut not incribs(?<!a)bbinfibbut not infab(?<![a-z])abc(?![a-z])abcwithout any letters before/afterRaw Markdown
# RegExp ## Character classes | Pattern | Description | | ------------- | ---------------------------------------- | | `.` | Any character, except newline | | `\w` | Word | | `\d` | Digit | | `\s` | Whitespace | | `\W` | Not word | | `\D` | Not digit | | `\S` | Not whitespace | | `[abc]` | Any of a, b, or c | | `[a-e]` | Characters between `a` and `e` | | `[1-9]` | Digit between `1` and `9` | | `[[:print:]]` | Any printable character including spaces | | `[^abc]` | Any character except `a`, `b` or `c` | ## Anchors | Pattern | Description | | ------- | ---------------------- | | `\G` | Start of match | | `^` | Start of string \* | | `$` | End of string \* | | `\A` | Start of string | | `\Z` | End of string | | `\z` | Absolute end of string | | `\b` | A word boundary | | `\B` | Non-word boundary | | `^abc` | Start with `abc` | | `abc$` | End with `abc` | For multiline patterns (`m` flag), `^` and `$` will act as start and end of line. ## Escaped characters | Pattern | Description | | ---------- | -------------------------------------- | | `\. \* \\` | Escape special character used by regex | | `\t` | Tab | | `\n` | Newline | | `\r` | Carriage return | ## Groups | Pattern | Description | | --------- | -------------------------------------------------------- | | `(abc)` | Capture group | | `(a\|b)` | Match `a` or `b` | | `(?:abc)` | Match `abc`, but don't capture | | `\1` | Substituted with text matched of the 1st capturing group | ## Quantifiers | Pattern | Description | | -------- | --------------------- | | `a*` | Match 0 or more | | `a+` | Match 1 or more | | `a?` | Match 0 or 1 | | `a{5}` | Match exactly 5 | | `a{,3}` | Match up to 3 | | `a{3,}` | Match 3 or more | | `a{1,3}` | Match between 1 and 3 | ## Lookahead & Lookbehind | Pattern | Description | | --- | --- | | `a(?=b)` | Match `a` in `baby` but not in `bay` | | `a(?!b)` | Match `a` in `Stan` but not in `Stab` | | `(?<=a)b` | Match `b` in `crabs` but not in `cribs` | | `(?<!a)b` | Match `b` in `fib` but not in `fab` | | `(?<![a-z])abc(?![a-z])` | Match `abc` without any letters before/after |