Hi, In xemacs-21.5.14 (and earlier versions as well) the following code is found in src/process-unix.c (previously called src/callproc.c) around line 1012 *SNIP* /* Close non-process-related file descriptors. It would be cleaner to close just the ones that need to be, but the following brute force approach is certainly effective, and not too slow. */ { int fd; for (fd = 3; fd < MAXDESC; fd++) retry_close (fd); } *SNIP* As the comment section explains, this is a very quick and dirty hack. In our case it prevents us from using xemacs as an editor in a sequence of pipe-connected programs. A == XEmacs == B | | +--------------+ We have program A create a set of pipes, then fork+exec XEmacs, which then uses (start-process ...) to create program B, which not only needs to communicate with the XEmacs session, but also with the original program A. Since XEmacs blatantly closes all filedescriptors except std{in,out,err}, program B can no longer use the pipe to program A. In xemacs-21.4.8 the comment header for this hack was slightly different: *SNIP* /* I can't think of any reason why child processes need any more than the standard 3 file descriptors. It would be cleaner to close just the ones that need to be, but the following brute force approach is certainly effective, and not too slow. */ *SNIP* After our explanation maybe you now see "why child processes need any more than the standard 3 file descriptors." and that just removing this line from the comment is not enough to fix the problem. As a comparison, check the same relevant section in GNU Emacs 21.2.21 which shows: *SNIP* emacs_close (0); emacs_close (1); emacs_close (2); dup2 (in, 0); dup2 (out, 1); dup2 (err, 2); emacs_close (in); emacs_close (out); emacs_close (err); *SNIP* They (GNU Emacs) only close the relevant filedescriptors, which is why our approach using pipes works perfectly with GNU Emacs. Please let me know if there is a version of XEmacs that addresses this issue, or whether you intend to fix it in some upcoming release. Until then we are unable to add xemacs to our list of supported editors which so far includes GNU Emacs, GVIM and Eclipse. Regards, -- Hayco de Jong, Centre for Mathematics and Computer Science (CWI) Kruislaan 413, NL 1098 SJ Amsterdam, The Netherlands room M336, phone +31 20 592-4007 url: www.cwi.nl/~jong e-mail: jong(a)cwi.nl