Re: Not missing, but very hard to see (was Re: Backslash missing in brace expansion)
On 12/12/19 9:57 PM, L A Walsh wrote: The backquote is in [6], and the backslash disappears, you just get the pair of quotes in [2] because that's how printf %q outputs an empty string. - I'm sorry, but you are mistaken. The characters from 'Z' (0x5A) through 'z' (0x61) are: 0x5A 0x5B 0x5C 0x5D 0x5E 0x5F 0x60 0x61 Z [ \ ] ^ _ ` a the backslash comes between the two square brackets. https://lists.gnu.org/archive/html/bug-bash/2019-12/msg00017.html -- ``The lyf so short, the craft so long to lerne.'' - Chaucer ``Ars longa, vita brevis'' - Hippocrates Chet Ramey, UTech, CWRUc...@case.eduhttp://tiswww.cwru.edu/~chet/
Re: Not missing, but very hard to see (was Re: Backslash missing in brace expansion)
On 12/12/19 9:57 PM, L A Walsh wrote:
>
>
> On 2019/12/12 13:01, Ilkka Virta wrote:
>> On 12.12. 21:43, L A Walsh wrote:
>>
>>> On 2019/12/06 14:14, Chet Ramey wrote:
>>>
>>> Seems very hard to print out that backquote though. Closest I got
>>> was bash converting it to "''":
>>>
>>
>> The backquote is in [6], and the backslash disappears, you just get
>> the pair of quotes in [2] because that's how printf %q outputs an
>> empty string.
>>
> -
>
> I'm sorry, but you are mistaken.
How so?
> The characters from 'Z' (0x5A) through 'z' (0x61) are:
>
> 0x5A 0x5B 0x5C 0x5D 0x5E 0x5F 0x60 0x61
> Z [ \ ] ^ _ ` a
>
> the backslash comes between the two square brackets.
>
> Position [6] is the "Grave Accent" (or backquote).
>
> It is quoted properly.
But... that's exactly what was said.
> As for %q printing an empty string for 0x5C
>
> "%q" causes printf to output the corresponding argument in a
> format that can be reused as shell input.
>
> For that string to be empty would mean there is no character at hex
> value 0x5C (unicode U+005C), which isn't so.
But there isn't. An empty string was passed as an argument to printf,
because the backslash was *converted* via escaping, into an empty
string, *before* it was passed on the command line as an argv element to
the printf builtin.
Do you think that because printf is a builtin, and you didn't use
/bin/printf, that somehow means it is exempt from the usual rule of how
shells work, and gets to see its own argv before the parser reinterprets it?
>>
read -r -a a< <(printf "%q " {Z..a})
my -p a
>>> declare -a a=([0]="Z" [1]="\\[" [2]="''" [3]="\\]" [4]="\\^" [5]="_"
>>> [6]="\\\`" [7]="a")
>>>
>>
>>
>>
--
Eli Schwartz
Bug Wrangler and Trusted User
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Re: Not missing, but very hard to see (was Re: Backslash missing in brace expansion)
On 2019/12/12 13:01, Ilkka Virta wrote:
On 12.12. 21:43, L A Walsh wrote:
On 2019/12/06 14:14, Chet Ramey wrote:
Seems very hard to print out that backquote though. Closest I got
was bash converting it to "''":
The backquote is in [6], and the backslash disappears, you just get the
pair of quotes in [2] because that's how printf %q outputs an empty string.
-
I'm sorry, but you are mistaken.
The characters from 'Z' (0x5A) through 'z' (0x61) are:
0x5A 0x5B 0x5C 0x5D 0x5E 0x5F 0x60 0x61
Z[\] ^ _ `a
the backslash comes between the two square brackets.
Position [6] is the "Grave Accent" (or backquote).
It is quoted properly.
As for %q printing an empty string for 0x5C
"%q" causes printf to output the corresponding argument in a
format that can be reused as shell input.
For that string to be empty would mean there is no character at hex
value 0x5C (unicode U+005C), which isn't so.
read -r -a a< <(printf "%q " {Z..a})
my -p a
declare -a a=([0]="Z" [1]="\\[" [2]="''" [3]="\\]" [4]="\\^" [5]="_"
[6]="\\\`" [7]="a")
Re: Not missing, but very hard to see (was Re: Backslash missing in brace expansion)
On 12.12. 21:43, L A Walsh wrote:
On 2019/12/06 14:14, Chet Ramey wrote:
Seems very hard to print out that backquote though. Closest I got
was bash converting it to "''":
The backquote is in [6], and the backslash disappears, you just get the
pair of quotes in [2] because that's how printf %q outputs an empty string.
read -r -a a< <(printf "%q " {Z..a})
my -p a
declare -a a=([0]="Z" [1]="\\[" [2]="''" [3]="\\]" [4]="\\^" [5]="_"
[6]="\\\`" [7]="a")
--
Ilkka Virta / itvi...@iki.fi
Re: Not missing, but very hard to see (was Re: Backslash missing in brace expansion)
On Thu, Dec 12, 2019 at 11:43:58AM -0800, L A Walsh wrote:
> > read -r -a a< <(printf "%q " {Z..a})
> > my -p a
> declare -a a=([0]="Z" [1]="\\[" [2]="''" [3]="\\]" [4]="\\^" [5]="_"
> [6]="\\\`" [7]="a")
Nice try. I guess the takeaway from this thread is: "You cannot mix
capital and lowercase letters in brace expansion. If you try, you
get garbage out."
Not missing, but very hard to see (was Re: Backslash missing in brace expansion)
On 2019/12/06 14:14, Chet Ramey wrote:
Seems very hard to print out that backquote though. Closest I got
was bash converting it to "''":
read -r -a a< <(printf "%q " {Z..a})
my -p a
declare -a a=([0]="Z" [1]="\\[" [2]="''" [3]="\\]" [4]="\\^" [5]="_"
[6]="\\\`" [7]="a")
#2 is where backslash would be and has been transliterated to the pair
of single quotes. Guess "" was too messy looking?
