standards/181240: /bin/sh choking on a certain construct

[Jilles Tjoelker]

On Mon, Aug 12, 2013 at 09:10:01PM +0000, Jens Schweikhardt wrote:
> The following reply was made to PR standards/181240; it has been noted
> by GNATS.

> From: Jens Schweikhardt <schweikh at schweikhardt.net>
> To: Tamas TEVESZ <ice at extreme.hu>
> Cc: freebsd-gnats-submit at FreeBSD.org
> Subject: Re: standards/181240: /bin/sh choking on a certain construct
> Date: Mon, 12 Aug 2013 23:06:43 +0200

>  On Mon, Aug 12, 2013 at 01:54:02PM +0000, Tamas TEVESZ wrote:

>  # >How-To-Repeat:
>  # /bin/sh -c 'echo foo || >&2 | cat'
>  # 
>  # (Or, if you have misc/mc installed, hit ^[3 on a .diff/.patch/.so etc. file for which mc calls /usr/local/libexec/mc/ext.d/misc.sh)

>  A simpler invocation is

>      $ >x | cat
>      Syntax error: "|" unexpected

>  If I read the SUS shell grammar correctly, a lone redirection cannot be
>  a simple command in a pipe, so this is an extension that the other
>  shells accept. I'm not sure if this is a particular useful extension.

I think the PR is valid. A lone redirection is a valid simple command,
everywhere a simple command may occur. In the grammar, the
simple_command consists of a single cmd_prefix which consists of a
single io_redirect.

I fixed this for & in 2010 and fixing it for | as well is not hard. The
same problem exists for ;; and ;&. See the below patch. I plan to commit
it soon.

Index: bin/sh/parser.c
===================================================================
--- bin/sh/parser.c	(revision 253911)
+++ bin/sh/parser.c	(working copy)
@@ -577,6 +577,9 @@ TRACE(("expecting DO got %s %s\n", tokname[got], g
 	case TSEMI:
 	case TAND:
 	case TOR:
+	case TPIPE:
+	case TENDCASE:
+	case TFALLTHRU:
 		/*
 		 * An empty command before a ; doesn't make much sense, and
 		 * should certainly be disallowed in the case of `if ;'.
Index: tools/regression/bin/sh/parser/only-redir2.0
===================================================================
--- tools/regression/bin/sh/parser/only-redir2.0	(revision 0)
+++ tools/regression/bin/sh/parser/only-redir2.0	(working copy)
@@ -0,0 +1,2 @@
+# $FreeBSD$
+</dev/null | :

Property changes on: tools/regression/bin/sh/parser/only-redir2.0
___________________________________________________________________
Added: svn:keywords
## -0,0 +1 ##
+FreeBSD=%H
\ No newline at end of property
Index: tools/regression/bin/sh/parser/only-redir3.0
===================================================================
--- tools/regression/bin/sh/parser/only-redir3.0	(revision 0)
+++ tools/regression/bin/sh/parser/only-redir3.0	(working copy)
@@ -0,0 +1,2 @@
+# $FreeBSD$
+case x in x) </dev/null ;; esac

Property changes on: tools/regression/bin/sh/parser/only-redir3.0
___________________________________________________________________
Added: svn:keywords
## -0,0 +1 ##
+FreeBSD=%H
\ No newline at end of property
Index: tools/regression/bin/sh/parser/only-redir4.0
===================================================================
--- tools/regression/bin/sh/parser/only-redir4.0	(revision 0)
+++ tools/regression/bin/sh/parser/only-redir4.0	(working copy)
@@ -0,0 +1,2 @@
+# $FreeBSD$
+case x in x) </dev/null ;& esac

Property changes on: tools/regression/bin/sh/parser/only-redir4.0
___________________________________________________________________
Added: svn:keywords
## -0,0 +1 ##
+FreeBSD=%H
\ No newline at end of property

-- 
Jilles Tjoelker