# string

### MODULE

string

### MODULE SUMMARY

String Processing Functions

### DESCRIPTION

This module contains functions for string processing.

### EXPORTS

`len(String) -> Length`

Types:

`String = string()`
`Length = integer()`

Returns the number of characters in the string.

`equal(String1, String2) -> bool()`

Types:

`String1 = String2 = string()`

Tests whether two strings are equal. Returns `true` if they are, otherwise `false`.

`concat(String1, String2) -> String3`

Types:

`String1 = String2 = String3 = string()`

Concatenates two strings to form a new string. Returns the new string.

`chr(String, Character) -> Index`
`rchr(String, Character) -> Index`

Types:

`String = string()`
`Character = char()`
`Index = integer()`

Returns the index of the first/last occurrence of `Character` in `String`. `0` is returned if `Character` does not occur.

`str(String, SubString) -> Index`
`rstr(String, SubString) -> Index`

Types:

`String = SubString = string()`
`Index = integer()`

Returns the position where the first/last occurrence of `SubString` begins in `String`. `0` is returned if `SubString` does not exist in `String`. For example:

    > string:str(" Hello Hello World World ", "Hello World").
    8

`span(String, Chars) -> Length`
`cspan(String, Chars) -> Length`

Types:

`String = Chars = string()`
`Length = integer()`

Returns the length of the maximum initial segment of String, which consists entirely of characters from (not from) Chars.

For example:

    > string:span("\t    abcdef", " \t").
    5
    > string:cspan("\t    abcdef", " \t").
    0

`substr(String, Start) -> SubString`
`substr(String, Start, Length) -> Substring`

Types:

`String = SubString = string()`
`Start = Length = integer()`

Returns a substring of `String`, starting at the position `Start`, and ending at the end of the string or at length `Length`.

For example:

    > substr("Hello World", 4, 5).
    "lo Wo"

`tokens(String, SeparatorList) -> Tokens`

Types:

`String = SeparatorList = string()`
`Tokens = [string()]`

Returns a list of tokens in `String`, separated by the characters in `SeparatorList`.

For example:

    > tokens("abc defxxghix jkl", "x ").
    ["abc", "def", "ghi", "jkl"]

`chars(Character, Number) -> String`
`chars(Character, Number, Tail) -> String`

Types:

`Character = char()`
`Number = integer()`
`String = string()`

Returns a string consisting of `Number` of characters `Character`. Optionally, the string can end with the string `Tail`.

`copies(String, Number) -> Copies`

Types:

`String = Copies = string()`
`Number = integer()`

Returns a string containing `String` repeated `Number` times.

`words(String) -> Count`
`words(String, Character) -> Count`

Types:

`String = string()`
`Character = char()`
`Count = integer()`

Returns the number of words in `String`, separated by blanks or `Character`.

For example:

    > words(" Hello old boy!", $o).
    4

`sub_word(String, Number) -> Word`
`sub_word(String, Number, Character) -> Word`

Types:

`String = Word = string()`
`Character = char()`
`Number = integer()`

Returns the word in position `Number` of `String`. Words are separated by blanks or `Character`s.

For example:

    > string:sub_word(" Hello old boy !",3,$o).
    "ld b"

`strip(String) -> Stripped`
`strip(String, Direction) -> Stripped`
`strip(String, Direction, Character) -> Stripped`

Types:

`String = Stripped = string()`
`Direction = left | right | both`
`Character = char()`

Returns a string, where leading and/or trailing blanks or a number of `Character` have been removed. `Direction` can be `left`, `right`, or `both` and indicates from which direction blanks are to be removed. The function `strip/1` is equivalent to `strip(String, both)`.

For example:

    > string:strip("...Hello.....", both, $.).
    "Hello"

`left(String, Number) -> Left`
`left(String, Number, Character) -> Left`

Types:

`String = Left = string()`
`Character = char`
`Number = integer()`

Returns the `String` with the length adjusted in accordance with `Number`. The left margin is fixed. If the `length(String)` < `Number`, `String` is padded with blanks or `Character`s.

For example:

    > string:left("Hello",10,$.).
    "Hello....."

`right(String, Number) -> Right`
`right(String, Number, Character) -> Right`

Types:

`String = Right = string()`
`Character = char`
`Number = integer()`

Returns the `String` with the length adjusted in accordance with `Number`. The right margin is fixed. If the length of `(String)` < `Number`, `String` is padded with blanks or `Character`s.

For example:

    > string:right("Hello", 10, $.).
    ".....Hello"

`centre(String, Number) -> Centered`
`centre(String, Number, Character) -> Centered`

Types:

`String = Centered = string()`
`Character = char`
`Number = integer()`

Returns a string, where `String` is centred in the string and surrounded by blanks or characters. The resulting string will have the length `Number`.

`sub_string(String, Start) -> SubString`
`sub_string(String, Start, Stop) -> SubString`

Types:

`String = SubString = string()`
`Start = Stop = integer()`

Returns a substring of `String`, starting at the position `Start` to the end of the string, or to and including the `Stop` position.

For example:

    sub_string("Hello World", 4, 8).
    "lo Wo"

`to_float(String) -> {Float,Rest} | {error,Reason}`

Types:

`String = string()`
`Float = float()`
`Rest = string()`
`Reason = no_float | not_a_list`

Argument `String` is expected to start with a valid text represented float (the digits being ASCII values). Remaining characters in the string after the float are returned in `Rest`.

Example:

              > {F1,Fs} = string:to_float("1.0-1.0e-1"),
              > {F2,[]} = string:to_float(Fs),
              > F1+F2.
              0.900000
              > string:to_float("3/2=1.5").
              {error,no_float}
              > string:to_float("-1.5eX").
              {-1.50000,"eX"}

`to_integer(String) -> {Int,Rest} | {error,Reason}`

Types:

`String = string()`
`Int = integer()`
`Rest = string()`
`Reason = no_integer | not_a_list`

Argument `String` is expected to start with a valid text represented integer (the digits being ASCII values). Remaining characters in the string after the integer are returned in `Rest`.

Example:

              > {I1,Is} = string:to_integer("33+22"),
              > {I2,[]} = string:to_integer(Is),
              > I1-I2.
              11
              > string:to_integer("0.5").
              {0,".5"}
              > string:to_integer("x=2").
              {error,no_integer}

### Notes

Some of the general string functions may seem to overlap each other. The reason for this is that this string package is the combination of two earlier packages and all the functions of both packages have been retained.

The regular expression functions have been moved to their own module `regexp` (see regexp(3)). The old entry points still exist for backwards compatibility, but will be removed in a future release so that users are encouraged to use the module `regexp`.

| Any undocumented functions in `string` should not be used.

### AUTHORS

Robert Virding - support@erlang.ericsson.se
Torbjorn Tornkvist - support@erlang.ericsson.se

stdlib 1.14
Copyright © 1991-2006 Ericsson AB