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ABAP Keyword Documentation →  ABAP - Reference →  Processing Internal Data →  Character String and Byte String Processing →  Expressions and Functions for String Processing →  Regular Expressions →  Syntax of Regular Expressions 

Single Character Patterns

Single characters are represented by literal characters or operators. If preceded by a backslash \, a special character of an operator is interpreted as a literal character. This applies in particular for the backslash \ itself, so that the regular expression \ is the same as the single character \. If the backslash is followed by a literal character, the backslash is ignored as if it does not exist.

Other versions: 7.31 | 7.40 | 7.54

Literal Characters

A literal character is a character that is not a special character, or a special character preceded by a backslash \, or enclosed between \Q ... \E. As a search string, a literal character matches the same single character exactly.


Note

Case-sensitivity can be controlled using the appropriate commands or methods.

Examples

The following table shows some results of a test that is case-sensitive.

Pattern text match
A A X
A a -
. . X
A AB -
AB AB X

The regular expression AB is a concatenation of two expressions for single characters.

Operators for Single Characters

These operators are made up of the special characters ., [, ], ^, and -. The last two are only effective as special characters in specific positions within [ ]. The special characters can be made into literal characters using the prefix \.

Placeholders for Single Characters

The special character . is a placeholder for any single character. The operator \C has the same effect as the special character .. A regular expression . or \C matches exactly one single character.

Examples

The following table shows some results of a test that is not case-sensitive.

Pattern Text match
. A X
\C a X
. AB -
.. AB X

The regular expression .. is a concatenation of two expressions for single characters.

Self-Defined Sets for Single Characters

The special characters [ ] can be placed around any number of literal characters or names for character classes (see below), and thus define a set of literal characters. A regular expression [...] matches exactly one single character listed as a literal character within the brackets, or which is contained in a specified character class. At least one literal character or one name for a character class (see below) must be contained within the brackets. A character [ or ], which is positioned directly after the opening bracket, is interpreted as a literal character. Some of the special characters that start with a backslash, such as \A or \Q, lose their special function within sets, and are interpreted as the simple literal character A or Q.

Examples

The following table shows some results from a test.

Pattern Text match
[ABC] B X
[ABC] ABC -
[AB][CD] AD X
[\d] 9 X

The regular expression [AB][CD] is a concatenation of two expressions for single characters.

Negation of a Self-Defined Set for Single Characters

If the character ^ is the first character in a self-defined set for single characters and is listed directly after [, it acts as a special character and negates the rest of the set of literal characters or character classes. A regular expression [^...] matches precisely one single character that is not specified as a literal character within the square brackets or that is not in a specified character class. A character ^ that is not listed directly after [ acts as a literal character.

Examples

The following table shows some results from a test.

Pattern Text match
[^ABC] B -
[^ABC] Y X
[^A][^B] BA X
[A^B] ^ X

The regular expression [^A][^B] is a concatenation of two expressions for single characters.

Ranges in a Self-Defined Set for Single Characters

If the character - is between two literal characters, it acts as a special character and defines a range between the literal characters. The range is the set of characters that is enclosed by literal characters in the code page of the current operating system. A regular expression [...-...] matches exactly one single character that is within the defined range. A character -, which is not between two literal characters, acts as a literal character. A literal character cannot be part of two ranges, for example, 'a-z-Z' is not a regular expression.

Examples

The following table shows some results from a test.

Pattern Text match
[A-Za-z0-9] B X
[A-Za-z0-9] 5 X
[A-Za-z0-9] # -
[A-Za-z0-9] - -
[A-Za-z0-9-] - X

In the last expression, the closing - does not act as a special character.

Character Classes

Within sets for single characters defined using [ ], predefined character classes can be specified for certain sets for single characters whose behavior can, however, depend on the language and platform.

  • [:alnum:]
    Set of all alphanumeric characters (union of [:alpha:] and [:digit:])
  • [:alpha:]
    Set of all uppercase and lowercase letters including language-specific special characters (umlauts, accents, diphthongs) without numbers.
  • [:blank:]
    Blank characters and horizontal tabs
  • [:cntrl:]
    Set of all control characters
  • [:digit:]
    Set of all digits 0 to 9
  • [:graph:]
    Set of all displayable characters except for blanks and horizontal tabs
  • [:lower:]
    Set of all lowercase letters including language-dependent special characters (umlauts, accents, diphthongs)
  • [:print:]
    Set of all displayable characters (union of [:graph:] and [:blank:])
  • [:punct:]
    Set of all punctuation characters
  • [:space:]
    Set of all blank characters, tabs, and carriage feeds
  • [:unicode:]
    Set of all characters with a character representation larger than 255 (only in Unicode systems)
  • [:upper:]
    Set of all uppercase letters including language-dependent special characters (umlauts, accents, diphthongs)
  • [:word:]
    Set of all alphanumeric characters including underscore _
  • [:xdigit:]
    Set of all hexadecimal digits ("0"-"9", "A"-"F", and "a"-"f")


Notes

  • Character classes only act within [ ] as specified. A regular expression [:digit:] does not define the set of all digits, but instead defines a character set consisting of ":", "d", "g", "i", and "t". To specify the set of all digits, use the regular expression [[:digit:]].

  • Due to their dependencies on language and platform, these character classes must be used with care.

Examples

The following table shows some results of a test that is case-sensitive.

Pattern Text match
[[:alnum:]] a X
[[:alnum:]] ; -
[[:alpha:]] 1 -
[[:digit:][:punct:]] X4 X
[[:digit:][:punct:]] . X
[[:lower:]] â X
[[:upper:]] Ä X

Abbreviations for Character Sets

For frequently used character sets, specific operators are available as abbreviations:

Character Set Abbr. Meaning
[[:digit:]] \d Placeholder for a digit
[^[:digit:]] \D Placeholder for a non-digit
[[:lower:]] \l Placeholder for a lowercase letter
[^[:lower:]] \L Placeholder for a character that is not a lowercase letter
[[:space:]] \s Placeholder for a blank character
[^[:space:]] \S Placeholder for a non-blank character
[[:upper:]] \u Placeholder for an uppercase letter
[^[:upper:]] \U Placeholder for a character that is not an uppercase letter
[[:word:]] \w Placeholder for an alphanumeric character plus underscore _
[^[:word:]] \W Placeholder for an non-alphanumeric character without underscore _


Note

If case is ignored by the ABAP statements FIND and REPLACE and when generating an object of the class CL_ABAP_REGEX, then \l and \u are equivalent to [[:alpha:]] or \L and \U is equivalent to [^[:alpha:]]. The special characters \w, \u, \l, \d, and \s can also be listed within sets [...]. Use of the special characters \W, \U, \L, \D, and \S within sets is not permitted and raises the exception CX_SY_INVALID_REGEX.

Examples

The following table shows some results of a test that is case-sensitive.

Pattern Text match
\d 4 X
\D ; X
\l u X
\l U -
\L S X
\s   X
\S # X
\u U X
\U . X
\w A X
\w 8 X
\W : X
\W _ -

Equivalence Classes

The operators [..] and [==] are reserved for future language enhancements and currently raise the exception CX_SY_INVALID_REGEX if used in sets.