read lisp objects from buffer

read lisp objects from buffer

[yuwen]

Dear all,

I have a file that contains lisp objects printed by function print:

((16746 13842 393000) "README.txt")

((16746 16787 969000) "/home/yuwen/.emacs")


I tried to read them back into lisp objects:

     (let ((buffer (find-file-noselect "~/src/el/tmp.txt")))
       (set-buffer buffer)
       (goto-char (point-min))
       (while (setq obj (read buffer))
          ;;; do something ))

but there's an error message :
   setq: End of file during parsing

So, what's the right way to read lisp objects from a file/buffer?

Best regards,
Dai Yuwen

Re: read lisp objects from buffer

[Kai Grossjohann]

yuwen <yuwen@micetek.com.cn> writes:

> I tried to read them back into lisp objects:
>
>     (let ((buffer (find-file-noselect "~/src/el/tmp.txt")))
>       (set-buffer buffer)
>       (goto-char (point-min))
>       (while (setq obj (read buffer))
>          ;;; do something ))
>
> but there's an error message :
>   setq: End of file during parsing
>
> So, what's the right way to read lisp objects from a file/buffer?

It is normal for (read buffer) to fail at the end of the buffer, so
you can catch this error using condition-case.

Or you can skip forward over whitespace and newlines after each read,
then check for eobp (end-of-buffer-p), and exit the loop if that is
true.

Or you prepend "(" and append ")" to the buffer contents, then invoke
read just once.  This will give you a list of objects.

Kai

Re: read lisp objects from buffer

[yuwen]

Kai Grossjohann wrote:

> yuwen <yuwen@micetek.com.cn> writes:
> 
> 
>>I tried to read them back into lisp objects:
>>
>>    (let ((buffer (find-file-noselect "~/src/el/tmp.txt")))
>>      (set-buffer buffer)
>>      (goto-char (point-min))
>>      (while (setq obj (read buffer))
>>         ;;; do something ))
>>
>>but there's an error message :
>>  setq: End of file during parsing
>>
>>So, what's the right way to read lisp objects from a file/buffer?
> 
> 
> It is normal for (read buffer) to fail at the end of the buffer, so
> you can catch this error using condition-case.
> 
> Or you can skip forward over whitespace and newlines after each read,
> then check for eobp (end-of-buffer-p), and exit the loop if that is
> true.
> 
> Or you prepend "(" and append ")" to the buffer contents, then invoke
> read just once.  This will give you a list of objects.
> 
Thank you. I use condition-case to protect the reading buffer process, 
and catch the `end-of-file' error:

       (condition-case nil
           (while (setq obj (read buffer))
              ;;; do something
         (end-of-file (kill-buffer buffer))))))


Best regards,
Dai Yuwen

Re: read lisp objects from buffer

[yuwen]

Kai Grossjohann wrote:

> yuwen <yuwen@micetek.com.cn> writes:
> 
> 
>>I tried to read them back into lisp objects:
>>
>>    (let ((buffer (find-file-noselect "~/src/el/tmp.txt")))
>>      (set-buffer buffer)
>>      (goto-char (point-min))
>>      (while (setq obj (read buffer))
>>         ;;; do something ))
>>
>>but there's an error message :
>>  setq: End of file during parsing
>>
>>So, what's the right way to read lisp objects from a file/buffer?
> 
> 
> It is normal for (read buffer) to fail at the end of the buffer, so
> you can catch this error using condition-case.
> 
> Or you can skip forward over whitespace and newlines after each read,
> then check for eobp (end-of-buffer-p), and exit the loop if that is
> true.
> 
> Or you prepend "(" and append ")" to the buffer contents, then invoke
> read just once.  This will give you a list of objects.
> 
> Kai
> 

Thank you. I use condition-case to protect the reading buffer process, 
and catch the `end-of-file' error:

       (condition-case nil
           (while (setq obj (read buffer))
              ;;; do something
         (end-of-file (kill-buffer buffer))))))


Best regards,
Dai Yuwen