Re: closing stdin (Re: _make suppress error on OpenBSD.)

["Bart Schaefer" <schaefer@candle.brasslantern.com>]

On May 10,  4:34am, Tanaka Akira wrote:
} Subject: closing stdin (Re: _make suppress error on OpenBSD.)
}
} > coulee% make awk: i/o error occurred while closing /dev/stdin
} 
} This problem is caused by the one true awk behavior.  (OpenBSD comes
} with the one true awk.)  The one true awk closes all file descriptors
} which should be opened when exit and complain if it causes an error.
} 
[...]
} 
} However, we can suppress the error by modifying each awk invocation,
} but I think that completion system should redirect stdin from
} /dev/null instead of closing it.

It's a little more complex than this.

Descriptor 0 is being closed by movefd(0) which is called from zle_main()
before executing any user-defined widget, completion or otherwise.  This
explains why it doesn't work to invoke e.g. vim from a widget function.

This has some odd side effects, including that assorted opens for things
like shared library loading and directory scans for path searching can end
up using FD 0 temporarily (look at strace output).  (Memory mapping of
autoloaded functions also sometimes gets FD 0 but immediately movefd()s it
elsewhere.)

It makes more sense to me from the standpoint of the shell's internals to
simply close FD 0 rather than reopen it on /dev/null.  On the other hand,
I've long forgotten (if I ever knew) why the stdin of ZLE functions is
closed.  (Zefram?)  It's trivial to reopen it again:

	function vi-vi-buffer() {
	    local tmp=${TMPPREFIX}${$}vi
	    print -R - $BUFFER >| $tmp
	    vi $tmp </dev/tty	# Reopen stdin closed by ZLE
	    BUFFER="$(<$tmp)"
	}
	zle -N vi-vi-buffer
	bindkey -v ; bindkey -a v vi-vi-buffer

On the other hand, it's probably a good idea that `exec < file' in a widget
doesn't change the whole shell's standard input, so duping and restoring FD
0 is good even if closing it may not be.

In any case, that latter suggests what I think is the best solution for the
completion system.

Index: Completion/Commands/_complete_help
===================================================================
@@ -3,6 +3,7 @@
 _complete_help() {
   setopt localoptions nullglob rcexpandparam extendedglob
   unsetopt markdirs globsubst shwordsplit nounset ksharrays
+  exec </dev/null	# ZLE closes stdin, which can cause errors
 
   local _sort_tags=_help_sort_tags text i j k
   typeset -A help_funcs help_tags help_sfuncs help_styles
Index: Completion/Core/_main_complete
===================================================================
@@ -18,6 +18,7 @@
 
 setopt localoptions nullglob rcexpandparam extendedglob
 unsetopt markdirs globsubst shwordsplit nounset ksharrays
+exec </dev/null	# ZLE closes stdin, which can cause errors
 
 local func funcs ret=1 tmp _compskip format nm \
       _completers _completer _completer_num curtag _comp_force_list \

-- 
Bart Schaefer                                 Brass Lantern Enterprises
http://www.well.com/user/barts              http://www.brasslantern.com