Re^4: Working with Binary Numbers

That's what bash docs says about the matter:

   Brace Expansion
       Brace expansion is a mechanism by which arbitrary strings may b
+e gener-
       ated.   This  mechanism is similar to pathname expansion, but t
+he file-
       names generated need not exist.  Patterns to be brace expanded 
+take the
       form of an optional preamble, followed by either a series of co
+mma-sep-
       arated strings or a sequence expression between a pair of brace
+s,  fol-
       lowed  by  an  optional  postscript.   The preamble is prefixed
+ to each
       string contained within the braces, and the postscript is then 
+appended
       to each resulting string, expanding left to right.

       Brace  expansions  may  be nested.  The results of each expande
+d string
       are not sorted;  left  to  right  order  is  preserved.   For  
+example,
       a{d,c,b}e expands into `ade ace abe'.

       A  sequence  expression takes the form {x..y}, where x and y ar
+e either
       integers or single characters.  When integers are supplied, the
+ expres-
       sion  expands  to each number between x and y, inclusive.  When
+ charac-
       ters are supplied, the expression expands  to  each  character 
+ lexico-
       graphically between x and y, inclusive.  Note that both x and y
+ must be
       of the same type.

       Brace expansion is performed before any other expansions, and a
+ny char-
       acters  special to other expansions are preserved in the result
+.  It is
       strictly textual.  Bash does not apply any syntactic interpreta
+tion  to
       the context of the expansion or the text between the braces.

       A  correctly-formed  brace  expansion must contain unquoted ope
+ning and
       closing braces, and at least one unquoted comma  or  a  valid  
+sequence
       expression.   Any incorrectly formed brace expansion is left un
+changed.
       A { or , may be quoted with a backslash to prevent its being co
+nsidered
       part  of  a brace expression.  To avoid conflicts with paramete
+r expan-
       sion, the string ${ is not considered eligible for brace expans
+ion.

       This construct is typically used as shorthand when the common p
+refix of
       the strings to be generated is longer than in the above example
+:

              mkdir /usr/local/src/bash/{old,new,dist,bugs}
       or
              chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}

       Brace  expansion  introduces  a  slight incompatibility with hi
+storical
       versions of sh.  sh does not treat opening or closing braces  s
+pecially
       when  they  appear as part of a word, and preserves them in the
+ output.
       Bash removes braces from words as a  consequence  of  brace  ex
+pansion.
       For  example,  a word entered to sh as file{1,2} appears identi
+cally in
       the output.  The same word is output as file1 file2 after expan
+sion  by
       bash.   If strict compatibility with sh is desired, start bash 
+with the
       +B option or disable brace expansion with the +B option to the 
+set com-
       mand (see SHELL BUILTIN COMMANDS below).
[download]

Comment on Re^4: Working with Binary Numbers Download Code

Replies are listed 'Best First'.
Re^5: Working with Binary Numbers ({not,here}) by tye (Sage) on Sep 25, 2007 at 15:18 UTC
Just to be clearer, if you read the first two sentences of the long section you quoted, it answers your original concern: Brace expansion is a mechanism by which arbitrary strings may be generated. This mechanism is similar to pathname expansion, but the filenames generated need not exist. So, no, this is not a bug. - tye	[reply]
Re^5: Working with Binary Numbers by ikegami (Patriarch) on Sep 25, 2007 at 15:19 UTC
If `bash` had any bearing in the matter — `glob` is based on `csh`'s expansion mechanism — it seems to me you just disproved yourself. "the filenames generated need not exist."	[reply] [d/l] [select]
Re^6: Working with Binary Numbers by salva (Canon) on Sep 25, 2007 at 15:36 UTC
it seems to me you just disproved yourself. yes, that was my intention :-) I was not trying to maintain my position but just to follow the "The documentation I could find isn't great on this point" on blokhead response. That's also why I used bash docs instead of csh, because they looked more clear to me and with regard to brace expansion, both shells behave the same.	[reply]
Re^7: Working with Binary Numbers by shoness (Friar) on Sep 25, 2007 at 17:52 UTC
Okay, so it's clear I don't understand how blokhead is using glob in this clever way. If I had files in the current directory that looked like one of the bit-vector patterns ("0000", "1-01", etc.) would that break his/her scheme? Can I trouble someone to break down that magic line of his: `my @data = qw( 000- 0101 011- 1-0- ); my @expanded = map { (my $s = $_) =~ s/-/{0,1}/g; glob($s) } @data;` [download] There is a CPAN module Text::Glob that looks like it does what this usage intends, without involving file globbing. The disadvantage is that it takes hundreds of lines to do what blokhead does in one line. That's Perl though! Thanks Again!	[reply] [d/l]
Re^8: Working with Binary Numbers by CountZero (Bishop) on Sep 25, 2007 at 20:48 UTC
Re^9: Working with Binary Numbers (" ) by tye (Sage) on Sep 26, 2007 at 14:50 UTC


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