List of Regular Expressions
Working with our application you can use the following regular expressions:
General Expressions
Maximum Quantifiers
Alternative and Grouping
Special notations with \
Examples
Additional examples of complex expressions
General Expressions | ||
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a | matches any value containing the letter a | apple, and, canal |
^ | matches the beginning of a string. | The expression ^A stands for the 'A' in "Anthony goes to Spain," but does not stand for it in "Susan goes to Africa" |
$ | matches the end of a string. | The expression t$ stands for the 't' in "seat," but does not stand for it in "teacher" |
. | matches any single character. | For example, .n will correspond to 'an' and 'on', but not to 'navy'. |
[...] | matches any of the characters in the sequence. | The expression [abd] allows entering words containing the letters in brackets: doll, bath, apricot. |
[^...] | matches any character except those in the sequence. | If you use expression [^abc] your respondents will not be allowed to input anything that contains letters a, b or c. |
Maximum Quantifiers | ||
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{m,n} | matches preceding character at least m, but not more than n times | For example, the expression a{1,3} means that you can enter words containing from 1 to 3 letters 'a' |
{m,} | matches preceding character m or more times | The expression a{2,} allows entering words containing 2 or more letters 'a' |
{,n} | matches preceding character from 0 to n times | The expression a{,2} allows you to enter words containing from 0 to 2 letters 'a' |
* | matches preceding character 0 or more times | The expression bo* allows you to input words containing only one letter 'b' and 0 or more letters 'o' |
+ | matches preceding character 1 or more times | The expression a+ allows entering words containing 1 or more letters 'a' |
? | matches preceding character 0 or 1 times | Using the expression e? you can input words containing 0 or 1 letter 'e' |
Alternative and Grouping | ||
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| | alternative | The expression green|red means that you can input either 'green' or 'red' |
( ) | grouping | The expression (ca)* means that * refers to all characters in brackets and you can input words containing 0 or more letters 'c' and 'a' |
Special notations with \ | ||
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\ | toggles off the interpretation of metacharacters and converts the following alphacharacters (w,d,s) in metacharacters. | For example, * is a special character that means 0 or more occurrences of the preceding character should be specified; for example, a* means match 0 or more a's. To match * literally, precede it with a backslash; for example, a\* matches 'a*'. |
\w | matches any single character classified as a "word" character: a letter or a number | The expression \w allows entering a letter or a number |
\d | matches any digit character, equivalent to [0-9] | The expression \d allows entering a number from 0 to 9. |
\s | matches any white space character (space, tab, new line, form feed) | The expression \s\w* allows to input only one white space and after it 0 or more letters or numbers. |
\W | matches any non-"word" character | The expression \W means that you can enter everything except letters and numbers. |
\D | matches any non-digit character | The expression \D allows entering everything except numbers. |
\S | matches any non-whitespace character | The expression \S allows to input everything except white spaces. |
Examples
^[0-5]?[0-9]$ - this simple expression allows to enter any whole number from 00 to 59. 1-digit numbers from 0 to 9 are allowed as well.
^ - asserts position at the beginning of the string
[0-5] - matches a single character in the range between '0' and '5'
? - matches the preceding element 0 or 1 times
[0-9] - matches a single character in the range between '0' and '9'
$ - asserts position at the end of the string
You can use regular expressions if you need to create a format that will allow users to enter only phone numbers of the following types:
(756)667-7832 or (756) 667 - 7832 ext. 234
In this case the formula will look like \(\d{3}\)\s?\d{3}\s?-\s?\d{4}\s?(\w+\.?\s?\d+)*
\(\) stands for brackets, \ is used to interpret () as simple brackets;
\d{3} refers to the sequence of three digits (numbers 0 to 9);
\d{4} refers to the sequence of four digits (numbers 0 to 9);
\s? means that there can be no spaces or only one space;
\w+ means that there can be one or more letters;
\d+ means that there can be one or more digits (numbers 0 to 9);
\.? stands for the dot, \ is used to interpret . as a simple dot and it means that there can be no dots or only one dot;
(\w+\.?\s?\d+)* means that the combination of letters and numbers can occur many times or never at all.
Additional examples of complex expressions
^\d+$ | Number | Any whole positive number + 0 |
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(0[1-9]|1[012])[- /.](0[1-9]|[12][0-9]|3[01])[- /.](19|20)\d\d | Date | Matches a date in mm/dd/yyyy format from between 1900-01-01 and 2099-12-31. '-', '/', '.' can be used as separators. |
^([a-z0-9]+(-[a-z0-9]+)*\.)+[a-z]{2,}$ | Domain name | Example: app.keysurvey.com |