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From: =?UTF-8?Q?=C3=98ystein_Walle?= <oystwa@gmail.com>
Date: Mon, 16 Dec 2013 20:10:49 +0100
Message-ID: <CAFaJEqs=P7yB-VGk=gJB2jzRf7zNiDkCuWWRADyY_xb52hGb_w@mail.gmail.com>
Subject: Read-only variables in emulation mode
To: zsh-workers@zsh.org
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Hi,

Consider the following:

    emulate sh -c '
    some_name() {
        status=3Dworld
        echo "hello $status"
    }
    some_name
    '

Running it gives:

    some_name:1: read-only variable: status

This is a problem if you source a "library" meant to be used by
different versions of different shells:

    $ cat =3Dgit-example
    #!/bin/zsh
    emulate sh -c '
    . git-sh-setup
    '
    ...
    require_work_tree
    ...
    $ git example
    die_with_status:1: read-only variable: status

A common idiom in (ba)sh scripting is to use _ as a throwaway in a
while-read loop:

    while read -r col1 _ col2; do
        echo "col1 =3D $col1 and col2 =3D $col2"
    done < three-columns.txt

This also fails with an equivalent message when used in sh emulation.

Is it fixable? (Is the general opinion that it needs fixing?). I
assume status and _ are meant to be writable in POSIX shells.

I suppose an idea would be for various variables to be writable within
emulate -c '...' and later in the functions defined therein. How this
would affect the rest of the shell is hard to say for me.

In the mean time, is there any way around it?

Thanks
=C3=98sse