On Tue, May 16, 2017 at 2:36 PM, Zoltán Herczeg <hzmes...@freemail.hu> wrote: [...] > bash version: GNU bash, version 4.3.11(1)-release (x86_64-pc-linux-gnu) > This command hangs in any directory on my machine (I don't have a directory > without a dot file): > > ls @(@()).
Yeah, I can reproduce the problem with bash 4.3.11. The empty globs make bash get stuck inside `extglob_skipname'. This was fixed in commit 3e8a02a68917250f088a500b09543255364f6f2b (http://git.savannah.gnu.org/cgit/bash.git/commit/?h=devel&id=3e8a02a68917250f088a500b09543255364f6f2b) > Yes, glibc seems correct. Do you mean this is a bug in the shell? I do not think it's a bug. In POSIX's "2.13.1 Patterns Matching a Single Character" (http://pubs.opengroup.org/onlinepubs/9699919799.2008edition/utilities/V3_chap02.html#tag_18_13_01), If an open bracket introduces a bracket expression as in XBD RE Bracket Expression , except that the <exclamation-mark> character ( '!' ) shall replace the <circumflex> character ( '^' ) in its role in a non-matching list in the regular expression notation, it shall introduce a pattern bracket expression. A bracket expression starting with an unquoted <circumflex> character produces unspecified results. Otherwise, '[' shall match the character itself. Then in "9.3.5 RE Bracket Expression" (http://pubs.opengroup.org/onlinepubs/9699919799.2008edition/basedefs/V1_chap09.html#tag_09_03_05), The character sequences "[." , "[=" , and "[:" ( <left-square-bracket> followed by a <period>, <equals-sign>, or <colon>) shall be special inside a bracket expression and are used to delimit collating symbols, equivalence class expressions, and character class expressions. These symbols shall be followed by a valid expression and the matching terminating sequence ".]" , "=]" , or ":]" , as described in the following items. So, from my interpretation you can't use the sequence <[><:> like that, and you should go with Daniel's suggestion instead (i.e. `a[[:alpha:]:abm[]') Here's how current shells treat this situation BTW: dualbus@debian:~$ for sh in mksh ksh93 dash posh bash; do echo $sh $($sh -c 'case a in [[:alpha:][:]) echo y;; esac'); done mksh ksh93 dash y posh bash dualbus@debian:~$ for sh in mksh ksh93 dash posh bash; do echo $sh $($sh -c 'case a in [[:alpha:]:[]) echo y;; esac'); done mksh ksh93 y dash y posh bash y As you can see, dash is the only one that treats `[[:alpha:][:]' as <alpha> OR <[> OR :
