Unsetting all elements of an associative array
I'm trying to use unset array[@] to empty an associative array, but something goes wrong. This behaves as expected: $ declare -A array; array[path/directory]=value This produces an error: $ declare -A array; unset array[@]; array[path/directory]=value bash: path/directory: division by 0 (error token is "directory") After unsetting all its elements, the array is not associative anymore? Using array=() empties the array correctly.
Re: Unsetting all elements of an associative array
On Wed, Feb 04, 2015 at 09:12:12AM +0100, isabella parakiss wrote: > I'm trying to use unset array[@] to empty an associative array, but something > goes wrong. What caused you to believe that would work? > This produces an error: > $ declare -A array; unset array[@]; array[path/directory]=value > bash: path/directory: division by 0 (error token is "directory") unset 'array[@]' appears to be exactly the same as unset 'array'. It completely eradicates the entire array, including the declaration that it is associative. Then when you do array[a/b]=c you are creating a new integer-indexed array. [a/b] becomes a math context, so it tries to divide the value of a by the value of b (using 0 if either of those is not set). On that note, today I learned that you are not allowed to use either * or @ as the index of an associative array in bash. I guess I can see why, but... that's probably going to break something some day.
Re: Unsetting all elements of an associative array
On 2/4/15 8:39 AM, Greg Wooledge wrote: > On that note, today I learned that you are not allowed to use either * > or @ as the index of an associative array in bash. What caused you to believe that would work? -- ``The lyf so short, the craft so long to lerne.'' - Chaucer ``Ars longa, vita brevis'' - Hippocrates Chet Ramey, ITS, CWRUc...@case.eduhttp://cnswww.cns.cwru.edu/~chet/
Re: Unsetting all elements of an associative array
On Wed, Feb 4, 2015 at 2:39 PM, Greg Wooledge wrote: > On that note, today I learned that you are not allowed to use either * > or @ as the index of an associative array in bash. I guess I can see why, > but... that's probably going to break something some day. :) of course you can ;-) declare -A a; a["@"]="right"; a["*"]="hoping that you are in an empty directory"; cheers, pg
Re: Unsetting all elements of an associative array
On Wed, Feb 04, 2015 at 03:37:07PM +0100, Piotr Grzybowski wrote: > On Wed, Feb 4, 2015 at 2:39 PM, Greg Wooledge wrote: > > > On that note, today I learned that you are not allowed to use either * > > or @ as the index of an associative array in bash. I guess I can see why, > > but... that's probably going to break something some day. > > :) > of course you can ;-) > > declare -A a; a["@"]="right"; a["*"]="hoping that you are in an empty > directory"; Huh, that's even stranger than I thought. imadev:~$ unset a; declare -A a; a=(["@"]=foo [!]=bar); declare -p a declare -A a='([@]="foo" ["!"]="bar" )' imadev:~$ unset a; declare -A a='([@]="foo" ["!"]="bar" )' bash: [@]="foo": invalid associative array key If the declare -p output is intended to be reusable shell code, then this is surely a bug. (Bash 4.3.30.)
Re: Unsetting all elements of an associative array
I think you are right, maybe this one should be considered:
diff --git a/lib/sh/shquote.c b/lib/sh/shquote.c
index fff4f81..de05f27 100644
--- a/lib/sh/shquote.c
+++ b/lib/sh/shquote.c
@@ -293,7 +293,7 @@ sh_contains_shell_metas (string)
case '(': case ')': case '<': case '>':
case '!': case '{': case '}': /* reserved words */
case '*': case '[': case '?': case ']': /* globbing chars */
- case '^':
+ case '^': case '@':
case '$': case '`': /* expansion chars */
return (1);
case '~': /* tilde expansion */
what do you think?
cheers,
pg
On Wed, Feb 4, 2015 at 3:42 PM, Greg Wooledge wrote:
> On Wed, Feb 04, 2015 at 03:37:07PM +0100, Piotr Grzybowski wrote:
>> On Wed, Feb 4, 2015 at 2:39 PM, Greg Wooledge wrote:
>>
>> > On that note, today I learned that you are not allowed to use either *
>> > or @ as the index of an associative array in bash. I guess I can see why,
>> > but... that's probably going to break something some day.
>>
>> :)
>> of course you can ;-)
>>
>> declare -A a; a["@"]="right"; a["*"]="hoping that you are in an empty
>> directory";
>
> Huh, that's even stranger than I thought.
>
> imadev:~$ unset a; declare -A a; a=(["@"]=foo [!]=bar); declare -p a
> declare -A a='([@]="foo" ["!"]="bar" )'
>
> imadev:~$ unset a; declare -A a='([@]="foo" ["!"]="bar" )'
> bash: [@]="foo": invalid associative array key
>
> If the declare -p output is intended to be reusable shell code, then
> this is surely a bug. (Bash 4.3.30.)
Re: If $HISTFILE is set to /dev/null and you execute more commands than $HISTFILESIZE, /dev/null is deleted.
On 2/1/15 1:52 AM, Jonathan Hankins wrote: > ​Right. My concern is that a potential exploit could inject a malicious > value for HISTFILE into the environment. I think (but may be wrong) that > HISTFILE is the only codepath in a default shell invocation that could > result in a silent writing to an arbitrary file without direct action on > the part of the user. If I can inject arbitrary variables into the environment, I'm not going to mess around with HISTFILE. I'm going straight to LD_PRELOAD or maybe LD_LIBRARY_PATH, game over. -- ``The lyf so short, the craft so long to lerne.'' - Chaucer ``Ars longa, vita brevis'' - Hippocrates Chet Ramey, ITS, CWRUc...@case.eduhttp://cnswww.cns.cwru.edu/~chet/
Re: Unsetting all elements of an associative array
On Wed, Feb 4, 2015 at 4:12 PM, isabella parakiss wrote:
> This produces an error:
> $ declare -A array; unset array[@]; array[path/directory]=value
> bash: path/directory: division by 0 (error token is "directory")
>
> After unsetting all its elements, the array is not associative anymore?
Logically that should only unset the elements of an array and not the
array variable
itself since '*' or '@' is more of a wildcard that represents the
indices. However, bash
does otherwise:
#define ALL_ELEMENT_SUB(c)((c) == '@' || (c) == '*')
...
if (ALL_ELEMENT_SUB (sub[0]) && sub[1] == 0) // If substring is
just '@' or '*'
{
unbind_variable (var->name); // It just removes it.
return (0);
}
Bash version is 4.3.33.
Re: Unsetting all elements of an associative array
On 2/4/15 9:42 AM, Greg Wooledge wrote: > imadev:~$ unset a; declare -A a; a=(["@"]=foo [!]=bar); declare -p a > declare -A a='([@]="foo" ["!"]="bar" )' > > imadev:~$ unset a; declare -A a='([@]="foo" ["!"]="bar" )' > bash: [@]="foo": invalid associative array key > > If the declare -p output is intended to be reusable shell code, then > this is surely a bug. (Bash 4.3.30.) You're right, it should be quoted. -- ``The lyf so short, the craft so long to lerne.'' - Chaucer ``Ars longa, vita brevis'' - Hippocrates Chet Ramey, ITS, CWRUc...@case.eduhttp://cnswww.cns.cwru.edu/~chet/
Re: Unsetting all elements of an associative array
On 2/4/15 10:27 AM, Piotr Grzybowski wrote:
> I think you are right, maybe this one should be considered:
>
> diff --git a/lib/sh/shquote.c b/lib/sh/shquote.c
> index fff4f81..de05f27 100644
> --- a/lib/sh/shquote.c
> +++ b/lib/sh/shquote.c
> @@ -293,7 +293,7 @@ sh_contains_shell_metas (string)
> case '(': case ')': case '<': case '>':
> case '!': case '{': case '}': /* reserved words */
> case '*': case '[': case '?': case ']': /* globbing chars */
> - case '^':
> + case '^': case '@':
> case '$': case '`': /* expansion chars */
> return (1);
> case '~': /* tilde expansion */
>
> what do you think?
It's a two-line fix, but that's the wrong place.
Chet
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRUc...@case.eduhttp://cnswww.cns.cwru.edu/~chet/
*** ../bash-4.3-patched/assoc.c 2011-11-05 16:39:05.0 -0400
--- assoc.c 2015-02-04 15:28:25.0 -0500
***
*** 437,440
--- 440,445
if (sh_contains_shell_metas (tlist->key))
istr = sh_double_quote (tlist->key);
+ else if (ALL_ELEMENT_SUB (tlist->key[0]) && tlist->key[1] == '\0')
+ istr = sh_double_quote (tlist->key);
else
istr = tlist->key;
