2012/9/6 Joshuah Hurst <joshhu...@gmail.com>:
> 2012/9/5 Roland Mainz <roland.ma...@nrubsig.org>:
>> 2012/9/5 Roland Mainz <roland.ma...@nrubsig.org>:
>>> 2012/9/5 David Korn <d...@research.att.com>:
>>> [CC:ing ast-developers@research.att.com so that the patch gets archived]
>>>> cc: g...@research.att.com olga.kryzhanov...@gmail.com
>>>> Subject: Re: New syntax for paths relative to directory fds
>>>> (~{dirfd}/foo/bar.txt) ...
>>>>> [Mostly Olga's idea (who is away and can't post anyway here since the
>>>>> AT&T spam filters have a grudge against her native name... ;-( )]
>>>>>
>>>>> Woud the following syntax for paths relative to a directory fd "dirfd"
>>>>> be possible without violating POSIX (right now the only way to archive
>>>>> this is to use /dev/fd/${dirfd}/ ... which works OK but may not be
>>>>> suiteable for a new version of the POSIX standard since POSIX does not
>>>>> mandate any absolute paths):
>>>>>
>>>>> ~{dirfd}/foo/bar/txt
>>>>>
>>>>> (where "dirfd" is a directory fd and "foo/bar/txt" is a path relative
>>>>> to this fd)
>>>>>
>>>>> Example usage:
>>>>> -- snip --
>>>>> # print contents of /etc/profile and /etc/ksh.kshrc
>>>>> redirect {dirfd}<"/etc"
>>>>> cat <~{dirfd}/profile
>>>>> cat <~{dirfd}/ksh.kshrc
>>>>> -- snip --
>>>>>
>>>>
>>>> That could be done. The code is in sh/macro.c sh_tilde_expand2().
>>> [snip]
>>>
>>> Attached (as "astksh_tilde_fd001.diff.txt") is a prototype patch.
>>> Technically it works without problems... but I'm not happy with the
>>> |static| variable |devfdname| (short: Ugly |static| variable... which
>>> means: Global variable (with function-local scope). Not thread-safe).
>>>
>>> Question: Is it _valid_ to allocate space from |shp->stk| and return
>>> the string as return value of |sh_tilde()| ? Who or what is going to
>>> deallocate the memory chunk ?
>>
>> Short answer from David:
>> -- snip --
>> Anything on shp->stk will get deleted when the command that it is
>> expanding completes.
>> -- snip --
>>
>> Attached (as "astksh_tilde_fd002.diff.txt") is a revised patch
>> (without function-static variables) per David&co.'s (code review)
>> feedback...
>
> Tried, tested, fell in love :)
>
> My only concern is that redirect {f}<>file never allowed plain numbers
> as f, i.e. redirect {512}<>file. IMO you should remove that, or add
> support that redirect {512}<>file works (I doubt David Korn is going
> to like that and I am not going to like it either).
Me neither. I think the symbolic version is better and prevents
programmers from hardcoding the fd numbers in scripts.
>
> If you are done please post to ast-us...@research.att.com to that
> Chester Ramey <chet.ra...@case.edu> can port this to bash :)
Agreed. I think this is very useful to make the long paths to
experiment data (often > 2k) we have more manageable in scripts.
Lionel
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