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read-line

read-line

type: function (subr) 
location: built-in
source file: xlfio.c  
Common LISP compatible: similar
supported on: all machines

SYNTAX

(read-line  [ <source> ]  )
        <source>        -       an optional source - must be a file pointer
                                or stream, the default is *standard-input*

DESCRIPTION

The READ-LINE function reads a single line from the specified <source>. The line read is returned as a string value for the result. The <source> may be a file pointer or a stream. If there is no <source>, *STANDARD-INPUT* is the default. If an end-of-file is encountered in the <source>, then NIL will be returned as the result.

EXAMPLES

(setq fp (open "f" :direction :output)) ; set up file
(print "fe fi" fp)                      ;
(print 12.34 fp)                        ;
(close fp)                              ;
                                        ;
(setq fp (open "f" :direction :input))  ; now read the file
(read-line fp)                          ; returns ""fe fi""     
(read-line fp)                          ; returns "12.34"
(read-line fp)                          ; returns NIL
(close fp)                              ; 

COMMON LISP COMPATIBILITY: The XLISP and Common LISP READ-LINE functions are compatible for simple cases. They both allow for the optional <source>. However, in Common LISP, there are addition parameters which occur right after <source>. So, when porting from Common LISP to XLISP, remember there are additional arguments in Common LISP's READ-LINE.

COMMON LISP COMPATIBILITY: Common LISP specifies that read operations with a <source> of NIL, will come from *STANDARD-INPUT*. XLISP does not read the input from *STANDARD-INPUT* with a <source> of NIL. Common LISP also specifies that a <source> of T will read from *TERMINAL-IO*. XLISP does not allow T as a valid argument for <source>.


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