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Re: Not missing, but very hard to see (was Re: Backslash missing in brace expansion)

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  Re: Not missing, but very hard to see (was Re: Backslash missing in brace expansion) L A Walsh <bash@tlinx.org> - 2019-12-12 18:57 -0800

#15724 — 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")
>>     
>
>
>   

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