Skip to main content
  • Bravura Security Fabric Documentation
  • Reference
  • Regular Expressions

Regular Expressions

Regular expressions provide a way to identify patterns of text in strings.

Bravura Security Fabric uses regular expressions to:

  • Match and block invalid passwords.

  • Identify users who it should not manage.

  • Extract text from Telnet/TN3270 screens in Telnet connector scripts.

  • Extract text from the output of password hashing programs in DBMS connector scripts.

Regular expressions use a shorthand of literal characters and special characters to define a pattern in a precise and compact way. Literal characters are case-sensitive. The regular expression parser used by Bravura Security Fabric uses the following special characters in literal strings:

Character

Purpose

Example

Match

.

Matches any single character

a.c

aac , abc , a1c , a2c

^

Beginning of a line

^hat

hat , hatch , not chat

$

End of a line

hat$

hat , chat , not hatch

|

Alternation

job | task

job or task

( )

Grouping

job(12 | 34)

job12 or job34

\

Treat the following special character literally

\$5\.6\\7

$5.6\7

The | alternates the longest possible string. That is, it matches job or task, and matches both jotask and jobask.

Grouping with ( ) limits the alternate branches.

Character sets

You can define a set of characters within a string. Character sets match any single character enclosed in square brackets [ ]. For example:

Expression

Match

j[oa]n

jon or jan

Use the - character between two characters in a set to indicate a range. A - character outside of a set, or at the beginning or end of a set, is treated literally. For example:

Expression

Match

[a-c]

a , b , or c

[1-3]

1 , 2 , or 3

[ab-]

a , b , or -

[B-D]-3

B-3 , C-3 , or D-3

If the first character in the set is ^, then the character set matches any character that is not in the list. For example:

Expression

Match

[^oa]

Any character except o and a

All other special characters lose their meaning when included in a character set. For example:

Expression

Match

^[^*\+.-]

Line must not start with *, \ , + , . ,or -

To include a literal ] in the character set, make it the first character in the set. It can also be excluded by following ^. The ] character is also treated literally outside of a set. For example:

Expression

Match

[^]a-]

Any character besides ] , a , and -

[]a]

] or a

[a]]

a]

Quantifiers

You can specify quantities of character sets, grouped characters, or individual characters. The quantifiers *, + , ? , and { } act on the preceding set, group, or individual character.

Character

Purpose

Example

Match

*

Specifies 0 or more consecutive occurrences

ab*c

ac , abc , abbbbc

+

Specifies 1 or more consecutive occurrences

ab+c

abc , abbbbc

?

Specifies 0 or 1 occurrence

colou?r (wo)?man

color or colour woman or man

{ x }

Exactly <x> occurrences

ab { 4 } c

abbbbc

{ x,y }

At least <x> , no more than <y> occurrences

ab { 2,4 } c

abbc , abbbc , abbbbc

{ x, }

At least <x> occurrences

ab { 2, } c

abbc , abbbc

{ ,x }

No more than <x> occurrences

ab { ,2 } c

ac , abc , or abbc

Shorthand expressions

The following expressions are shorthand for longer or more complex regular expressions:

Expression

Purpose

Example

Match

[:alpha:]

Matches must consist of letters.

[:alpha:]8,16

aBcmGLeEhhi

[:digit:]

Matches must consist of digits. [:digit:] is equivalent to [:d:] and \ d.

[[:digit:]]+

2962954576

[:upper:]

Matches must consist of uppercase characters.

[[:upper:][:digit:]]+

9DDD4MLAG13

[:alnum:]

Matches must be alphanumeric. [:alnum:] is short hand for [a-zA-Z0-9] in the ascii character set, but the use of [:alnum:] is preferred for compatibility with other languages and character sets.

[:alnum:]7[^[:digit:]]

a3dM9DD+

Examples

Only allow letters, numbers, exclamation point, and period

^[a-zA-Z0-9!.]⋆$

At most 8 characters long

^.,8$

Must start with a letter

^[a-zA-Z]

Must have a number

[0-9]

Must end in -admin or -test

(-admin | -test)$

Must begin with three capital letters and an underscore

^[A-Z] { 3 } _

See also

Bravura Security Fabric uses the ECMAScript regular expression grammar. For more information on regular expressions supported by Bravura Security Fabric, see:

In this section: