This module has been obsoleted by the re module and will be removed in a future release.
This module has been obsoleted by the re module and will be removed in a future release.
This module contains functions for regular expression matching and substitution.
match(String, RegExp) -> MatchRes
Types:
String = RegExp = string()
MatchRes = {match,Start,Length} | nomatch | {error,errordesc()}
Start = Length = integer()
Finds the first, longest match of the regular expression RegExp in String. This function searches for the longest possible match and returns the first one found if there are several expressions of the same length. It returns as follows:
first_match(String, RegExp) -> MatchRes
Types:
String = RegExp = string()
MatchRes = {match,Start,Length} | nomatch | {error,errordesc()}
Start = Length = integer()
Finds the first match of the regular expression RegExp in String. This call is usually faster than match and it is also a useful way to ascertain that a match exists. It returns as follows:
matches(String, RegExp) -> MatchRes
Types:
String = RegExp = string()
MatchRes = {match, Matches} | {error, errordesc()}
Matches = list()
Finds all non-overlapping matches of the expression RegExp in String. It returns as follows:
sub(String, RegExp, New) -> SubRes
Types:
String = RegExp = New = string()
SubRes = {ok,NewString,RepCount} | {error,errordesc()}
RepCount = integer()
Substitutes the first occurrence of a substring matching RegExp in String with the string New. A & in the string New is replaced by the matched substring of String. \& puts a literal & into the replacement string. It returns as follows:
gsub(String, RegExp, New) -> SubRes
Types:
String = RegExp = New = string()
SubRes = {ok,NewString,RepCount} | {error,errordesc()}
RepCount = integer()
The same as sub, except that all non-overlapping occurrences of a substring matching RegExp in String are replaced by the string New. It returns:
split(String, RegExp) -> SplitRes
Types:
String = RegExp = string()
SubRes = {ok,FieldList} | {error,errordesc()}
Fieldlist = [string()]
String is split into fields (sub-strings) by the regular expression RegExp.
If the separator expression is " " (a single space), then the fields are separated by blanks and/or tabs and leading and trailing blanks and tabs are discarded. For all other values of the separator, leading and trailing blanks and tabs are not discarded. It returns:
sh_to_awk(ShRegExp) -> AwkRegExp
Types:
ShRegExp AwkRegExp = string()
SubRes = {ok,NewString,RepCount} | {error,errordesc()}
RepCount = integer()
Converts the sh type regular expression ShRegExp into a full AWK regular expression. Returns the converted regular expression string. sh expressions are used in the shell for matching file names and have the following special characters:
It may sometimes be more practical to use sh type expansions as they are simpler and easier to use, even though they are not as powerful.
Types:
RegExp = string()
ParseRes = {ok,RE} | {error,errordesc()}
Parses the regular expression RegExp and builds the internal representation used in the other regular expression functions. Such representations can be used in all of the other functions instead of a regular expression string. This is more efficient when the same regular expression is used in many strings. It returns:
format_error(ErrorDescriptor) -> Chars
Types:
ErrorDescriptor = errordesc()
Chars = [char() | Chars]
Returns a string which describes the error ErrorDescriptor returned when there is an error in a regular expression.
The regular expressions allowed here is a subset of the set found in egrep and in the AWK programming language, as defined in the book, The AWK Programming Language, by A. V. Aho, B. W. Kernighan, P. J. Weinberger. They are composed of the following characters:
The escape sequences allowed are the same as for Erlang strings:
To make these functions easier to use, in combination with the function io:get_line which terminates the input line with a new line, the $ characters also matches a string ending with "...\ ". The following examples define Erlang data types:
Atoms [a-z][0-9a-zA-Z_]* Variables [A-Z_][0-9a-zA-Z_]* Floats (\+|-)?[0-9]+\.[0-9]+((E|e)(\+|-)?[0-9]+)?
Regular expressions are written as Erlang strings when used with the functions in this module. This means that any \ or " characters in a regular expression string must be written with \ as they are also escape characters for the string. For example, the regular expression string for Erlang floats is: "(\\+|-)?[0-9]+\\.[0-9]+((E|e)(\\+|-)?[0-9]+)?".
It is not really necessary to have the escape sequences as part of the regular expression syntax as they can always be generated directly in the string. They are included for completeness and can they can also be useful when generating regular expressions, or when they are entered other than with Erlang strings.