[ Character I/O | The ECLiPSe Built-In Predicates | Reference Manual | Alphabetic Index ]

# read_string(+Delimiters, ?Length, -String)

Reads a string from the input stream up to a delimiter or up to a specified length

Delimiters
  String or atom.
Length
  Integer or variable.
String
  String or variable.

## Description

A string of characters is read from the input up to one character which occurs in the delimiter string Delimiters. This character is also consumed, but does not appear in the string which is unified with String. Two symbolic Delimiters can be specified:

        end_of_line   a newline or carriage-return/newline sequence
        end_of_file   the end of the file/input

End of file always acts like a delimiter.

If Length is a variable, it is unified with the length of the string String. If Length is an integer, the number of characters read from the input is limited by the Length.

### Modes and Determinism

- read_string(+, +, -) is semidet
- read_string(+, -, -) is semidet

### Fail Conditions

There is nothing to read, i.e. the stream is at end_of_file

### Exceptions

(4) instantiation fault
  Delimiters is not instantiated.
(5) type error
  Delimiters is not a string or atom.
(5) type error
  Length is not an atom or an integer.
(5) type error
  String is not an atom or a string.
(6) out of range
  Delimiters is an atom but not a valid symbolic delimiter.
(190) end of file reached
  End of file was encountered before reading any character.
(198) reading past the file end
  Trying to read even after the error 190 was raised.

## Examples

       Equivalent to read_string(input, Delimiters, Length, String).  (see
       read_string/4 for details).

## See Also

read_string / 4, read_token / 2, read_token / 3, open / 3