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Re: redirections preceded by a word with builtins inconsistent

From: adonis papaderos
Subject: Re: redirections preceded by a word with builtins inconsistent
Date: Sun, 22 May 2016 21:48:47 +0300

I had read this before sending this message. The discussion you mention concerns leaking named redirections from function calls. This is not what I was trying to say. I was talking about the difference in behaviour between the creation and the destructions of the fd. There is also the difference in behaviour between builtins and external programs that confuses me, but in this case I just wanted to understand the creation and the destruction. Imho, since it is by design, there should be a mention of this is the documentation. I'm probably nitpicking, but the reasoning behind this is not obvious to me.


2016-05-22 21:06 GMT+03:00 Chet Ramey <address@hidden>:
On 5/21/16 5:16 PM, adonis papaderos wrote:

> Bash Version: 4.3
> Patch Level: 42
> Release Status: release
> Description:
>     When using redirections preceded by a word on builtins
>         'i.e. : {varname}<&1'
>         the redirection persists to the current shell.

This is by design, and has been discussed previously.  One such discussion
starts at http://lists.gnu.org/archive/html/bug-bash/2016-01/msg00156.html.
Maybe it should only do it when preceded by `exec', but it never has.

>         Later using {varname}<&- does not close fd.

You don't precede it with an `exec', so it doesn't affect the current
shell.  So-called `null' commands with redirections are executed in
subshells.  This is where you need the `exec'.

``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU    address@hidden    http://cnswww.cns.cwru.edu/~chet/

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