[gentoo-dev] Re: [PATCH 1/2] Introduce multibuild_merge_root() to merge interim installs.

[Alec Warner <antarus@gentoo.org>]

On Sat, Mar 23, 2013 at 11:57 AM, Jonathan Callen <abcd@gentoo.org> wrote:
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> On 03/23/2013 01:44 PM, Alec Warner wrote:
>> On Sat, Mar 23, 2013 at 9:26 AM, Michał Górny <mgorny@gentoo.org>
>> wrote:
>>> +                       # Close the lock file when we are done
>>> with it. +                       # Prevents deadlock if we aren't
>>> in a subshell. +                       eval "exec ${lock_fd}>&-"
>>
>> Not following this bit.
>>
>> The bash manpage says N>&DIGIT- redirects fd DIGIT to fd N. N may
>> be unspecified and defaults to 1.
>>
>> It doesn't say what happens if DIGIT is unspecified. Nor does it
>> say it closes any file descriptors.
>>
>
> The relevant section of bash(1) is reproduced below:
>
>    Duplicating File Descriptors
>        The redirection operator
>
>               [n]<&word
>
>        is used to duplicate input file descriptors.  If word expands to
>        one or more digits, the file descriptor denoted by n is made to
>        be a copy of that file descriptor.  If the digits in word do not
>        specify a file descriptor open for input, a redirection error
>        occurs.  If word evaluates to -, file descriptor n is closed.
>        If n is not specified, the standard input (file descriptor 0) is
>        used.
>
>        The operator
>
>               [n]>&word
>
>        is used similarly to duplicate output file descriptors.  If n is
>        not specified, the standard output (file descriptor 1) is used.
>        If the digits in word do not specify a file descriptor open for
>        output, a redirection error occurs.  As a special case, if n is
>        omitted, and word does not expand to one or more digits, the
>        standard output and standard error are redirected as described
>        previously.
>
> While the outcome of n>&- is not specified directly in the man page,
> it is treated exactly as n<&- is.

Ahh, I was reading:

   Moving File Descriptors
       The redirection operator

              [n]<&digit-

       moves the file descriptor digit to file descriptor n, or the
standard input (file descriptor 0) if n is not specified.  digit is
closed
       after being duplicated to n.

       Similarly, the redirection operator

              [n]>&digit-

       moves the file descriptor digit to file descriptor n, or the
standard output (file descriptor 1) if n is not specified.

I see where i went wrong now ;)

>
> - --
> Jonathan Callen
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