Greetings! Matt Kaufmann <[EMAIL PROTECTED]> writes:
> Hi -- > > Thank you for the quick reply! > > I realize now that I can just handle this issue at the ACL2 level, by > causing an error on an attempt to call open on a string starting with > the | character. (As a possibly humorous aside: I forgot to quote > (open "|kill -9 -1") as a format argument in my error message, and > sure enough, when testing an illegal open I managed to log myself out! > Ouch.) > OK. Other options in case you find them useful are 1) runtime setting disabling piped opens 2) compile time setting doing the same 3) running the pipe in a sanitized subshell incapable of interfering with the parent. (my favorite) > But here are some observations in case you find them helpful. > > I guess it wouldn't help me to check the type of the returned stream, > since I want to avoid executing code after the pipe. Anyhow, for what > it's worth, it looks like GCL 2.7.0 ANSI (a version Boyer sent me > yesterday) returns FILE-STREAM for the type of a stream connected to > other than a file. > > >(setq str (open "|cat tmp" :direction :input)) > > #<input stream "|cat tmp"> > > >(type-of str) > > FILE-STREAM > > > > > But actually, the ANSI spec for open seems to require a FILE-STREAM > (or nil) to be returned; see > http://www.lisp.org/HyperSpec/Body/fun_open.html#open. So I'm not > sure that the above OPEN is legal. > Well, if we must return a file-stream, we must. I think a pipe fits that concept, at least within the unix philosophy. Perhaps an additional predicate 'seekable-stream-p? There are all sorts of objects one might open that are not seekable. In fact, I'm not sure CL supports file repositioning more than one char at a time. char devices (e.g. /dev/random), fifos, sockets, etc. Take care, > Thanks -- > -- Matt > Cc: [EMAIL PROTECTED], [EMAIL PROTECTED], gcl-devel@gnu.org > From: Camm Maguire <[EMAIL PROTECTED]> > Date: 30 Oct 2006 14:54:44 -0500 > X-SpamAssassin-Status: No, hits=-2.5 required=5.0 > X-UTCS-Spam-Status: No, hits=-240 required=200 > > Greetings! > > IMHO, this is a pretty useful feature of GCL, which helps in > auto-decompressing compressed files, outputting straight to a printer, > etc. It also matches the unix convention of "pipes as file objects" > -- e.g. gnuplot and many other programs work this way. > > Perhaps some predicate on the stream would help? If memory serves, > the ansi standard has such notions, e.g. 'file-streams'. > > Take care, > > Matt Kaufmann <[EMAIL PROTECTED]> writes: > > > Hi, Camm -- > > > > Bob Boyer pointed out something scary to me back in May, and I'm > > finally getting around to asking you about it. He noticed that by > > executing (open "|kill -9 -1") in GCL, you can logout and kill all > > your processes! Or just start up GCL in Linux, suspend and use ps to > > get the process id -- say it's 23327 -- and then do this to kill your > > GCL: > > > > (open "|kill -9 23327") > > > > This is scary from an ACL2 perspective, when I'd expected that open > > just does an open. I suppose we could look for a first character of > > #\| and cause an error in that case. But maybe you want to consider > > eliminating this GCL feature? > > > > Thanks -- > > -- Matt > > > > > > > > -- > Camm Maguire [EMAIL > PROTECTED] > ========================================================================== > "The earth is but one country, and mankind its citizens." -- Baha'u'llah > > > -- Camm Maguire [EMAIL PROTECTED] ========================================================================== "The earth is but one country, and mankind its citizens." -- Baha'u'llah _______________________________________________ Gcl-devel mailing list Gcl-devel@gnu.org http://lists.gnu.org/mailman/listinfo/gcl-devel
