non-interactive build question

[Grant Edwards]

On 2013-10-16, Qais Yousef <Qais.Yousef at imgtec.com> wrote:

>> This seems to work but I would still like to try and find a way to
>> generate the .config file I want without having to run menuconfig at
>> all.  I think what I would really like is something like:
>
> You'll only have to run menuconfig manually once.
>
> Once you have a good set of config files it should be easy to
> manipulate them to produce other variants you like. I can't see how
> you can avoid the first manual menuconfig step personally.

Manipulating .config files programmatically is pretty easy.

The shell script I use to build a buildroot-based system doesn't
require any use of menuconfig.

The one thing you have to remember when manipulating a .config file is
that changing a config value often has side effects. For example: when
you want to enable and configure a previously disabled subsystem, you
have to do it in stages:

  1) Enable the subsystem

  2) Run "make oldconfig" to make the subsystem's configuration items
     appear in the .config file with default values.

  3) Enable/Disable/Set the subsystem's configuration items.

Depending on how the configuration items are defined, you can end up
with this process nesting several levels deep.
  
To that end, here are 3 bash functions I use:

set -o nounset
set -o errexit

# low level functions used to manipulate linux kernel-style .config
# files.

function SyncConfig()
{
    yes '' | $Make oldconfig >/dev/null
}

# By default, UnsetValue and SetValue will, after modifying the
# .config file, do a "make oldconfig" to re-normalize the .config
# file. Use the -n option to prevent that.

function UnsetValue()
{
    dosync=y
    test "$1" = '-n' && { dosync=n; shift; }
    Variable="$1"
    echo "UnsetValue $Variable"
    sed -i "s/^${Variable}=.*/# ${Variable} is not set/g" .config
    test $dosync = y && SyncConfig
    return 0
}

function SetValue()
{
    dosync=y
    test "$1" = '-n' && { dosync=n; shift; }
    Variable="$1"
    # default value is 'y'
    Value="${2-y}"
    echo "SetValue $Variable $Value"
    # if value isn't 'y', then put it in double quotes
    test "$Value" != y && Value="\"$Value\""
    # escape any slashes
    Value=${Value//\//\\\/}
    sed -i "s/^${Variable}=.*/${Variable}=${Value}/g" .config
    sed -i "s/^# ${Variable} is not set.*/${Variable}=${Value}/g" .config
    test $dosync = y && SyncConfig
    return 0
}

Then you can make function calls like this in a build script:

  TPath=/path/to/my/toolchain

  SetValue      BR2_TOOLCHAIN_EXTERNAL_PATH "$TPath"

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Grant Edwards               grant.b.edwards        Yow! Now that I have my
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