21.2.22 read-line [Function]

read-line &optional input-stream eof-error-p eof-value recursive-p
⇒ line, missing-newline-p

Arguments and Values::

input-stream—an input stream designator. The default is standard input.

eof-error-p—a generalized boolean. The default is true.

eof-value—an object. The default is nil.

recursive-p—a generalized boolean. The default is false.

line—a string or the eof-value.

missing-newline-p—a generalized boolean.

Description::

Reads from input-stream a line of text that is terminated by a newline or end of file.

If recursive-p is true, this call is expected to be embedded in a higher-level call to read or a similar function used by the Lisp reader.

The primary value, line, is the line that is read, represented as a string (without the trailing newline, if any). If eof-error-p is false and the end of file for input-stream is reached before any characters are read, eof-value is returned as the line.

The secondary value, missing-newline-p, is a generalized boolean that is false if the line was terminated by a newline, or true if the line was terminated by the end of file for input-stream (or if the line is the eof-value).

Examples::

 (setq a "line 1
 line2")
⇒  "line 1
 line2"
 (read-line (setq input-stream (make-string-input-stream a)))
⇒  "line 1", false
 (read-line input-stream)
⇒  "line2", true
 (read-line input-stream nil nil)
⇒  NIL, true

Affected By::

*standard-input*, *terminal-io*.

Exceptional Situations::

If an end of file_2 occurs before any characters are read in the line, an error is signaled if eof-error-p is true.

See Also::

read

Notes::

The corresponding output function is write-line.