On Fri, Jan 19, 2007 at 11:07:14AM -0500, Adam wrote: > Darrin Chandler <[EMAIL PROTECTED]> wrote: > > > On Thu, Jan 18, 2007 at 05:17:50PM -0500, Adam wrote: > > > Why does fopen()ing a directory for reading succeed instead of failing > > > with EISDIR? This has the possibly unexpected consequence of letting > > > you pass yyin to yylex() as a fopen()ed directory, which then thinks it > > > finished successfully because fread() returns 0 immediately. > > > > Directories are files and can be open(2)ed as such for reading. > > We're not talking about the low level open() interface, we're talking > about the abstracted fopen() wrapper. You can't use fread() on a > fopen()ed directory, and when passed a FILE * you can't tell wether its > a directory or just an empty file. If you can't fread() from a stream > that is associated with a directory, then why associate the stream with > a directory in the first place? > > Adam > >
C* doesn't know about directories and makes no assumptions about them. Directories in Unix happen to be implemented as a file, so that's perfectly legal. Reading and writing from/to the file depends on the OS, and the C* standard doesn't require that this must succeed/fail. If and how it fails is implemented by the OS and documented here: http://www.opengroup.org/onlinepubs/009695399/functions/fopen.html use stat(2) before you fopen anything to make sure it's not a dir/device/etc (race condition...). Tobias *C89 + C99
