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Re: readlink null termination problem

On Mon, 5 Jan 2004, Christopher Faylor wrote:

> On Tue, Jan 06, 2004 at 08:17:14AM +0800, peter garrone wrote:
> >I was having a problem with mkcramfs on cygwin creating symbolic links
> >for the compressed linux filesystem.
> >
> >mkcramfs uses malloc to allocate a buffer that it sends to the readlink function in cygwin
> >That function uses memcpy to do a copy of the link into a buffer.
> >Neither mkcramfs or readlink is null-terminating the string representing the link.
> >
> >Probably both are at fault. I have fixed my problem by zeroing the buffer in mkcramfs
> > before calling readlink, but it would probably be beneficial if readlink terminates
> > the returned string, if there is room.
>        readlink - read value of a symbolic link
>        #include <unistd.h>
>        int readlink(const char *path, char *buf, size_t bufsiz);
>        readlink  places  the  contents of the symbolic link path in the buffer
>        buf, which has size bufsiz.  readlink does not append a  NUL  character
>        to  buf.   It will truncate the contents (to a length of bufsiz charac-
>        ters), in case the buffer is too small to hold all of the contents.

And, to ward off the obvious next question:

       The  call  returns  the  count of characters placed in the
       buffer if it succeeds, or a -1 if an error occurs, placing
       the error code in errno.

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