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Re: Bash 3 breaks array expansion


From: William Park
Subject: Re: Bash 3 breaks array expansion
Date: 12 Aug 2004 21:41:02 GMT
User-agent: tin/1.6.2-20030910 ("Pabbay") (UNIX) (Linux/2.6.7 (i686))

Roy Marples <address@hidden> wrote:
> Description:
>         Bash 3 breaks array expansion
> 
> Repeat-By:
>         #!/bin/bash
>         x=(one two)
>         echo address@hidden:1}
>         # prints nothing in bash 3
>         # prints two in bash 2
> 
>         x=(one two three)
>         echo address@hidden:1}
>         # prints two three as expected in bash 2
> 
> Fix:
>         (really a work around)
>         #!/bin/bash
>         x=(one two)
>         x=("address@hidden" "xxx")
>         echo address@hidden:1:address@hidden - 2}

It is broken in verify_substring_values().  In Bash-3.0, the first
argument is array index, and the second argument is number of elements
(in storage, not in index).  For your case, '1' is tested against
'max_index' which is 1, so it exits.

That is why, you get
    x=(one two [9]=nine)
    echo ${x[*]:1}      --> 'two nine', as expected
    echo ${x[*]:1:2}    --> 'two nine', but 'two' was expected
    echo ${x[*]:2:2}    --> 'nine', but '' was expected
even though x[9] is outside of the index range specified.


Fix1:
    case VT_ARRAYVAR:
      a = (ARRAY *)value;
      /* For arrays, the first value deals with array indices. */
-      len = array_max_index (a);       /* arrays index from 0 to n - 1 */
+      len = array_max_index (a) + 1;   /* arrays index from 0 to n - 1 */
      break;


Fix2:
    Use positional parameter,
        set one two 
        echo ${*:2}

-- 
William Park <address@hidden>
Open Geometry Consulting, Toronto, Canada




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