The purpose of this patch is to allow exporting of variables to parent
environment variable scopes, not only to the nested scopes.
This does not break compatibility with any existing modules or GRUB
configuration files/scripts. The introduced changed are:
* The ‘export’ command became an extcmd. This was done to process the
newly added options. This also added ‘--help’ and ‘--usage’ options to
the command, but I think that it will be helpful to users of the GRUB.
* The ‘export’ command accepts an ‘-g’/‘--global’ option now. It causes
exporting the given variables not only to the newly created scopes,
but also to any parent scope (recursively), when this scope exits.
* To complement this behaviour, the option ‘-u’/‘--unexport’ was added to
the ‘export’ command. Using this option undoes the exporting of the
variable, so it becomes local again.
* A function ‘grub_env_set_export_mode’ and its accompanying enum was
created to allow un-exporting variables and making them global.
These changes were performed to allow me creating complex menu-based
pre-boot configuration interface for a live disk image on which I am
currently working. With these changes, it is possible to create a
submenu containing options that do not cause the bootloader to boot
directly, but only affect further selected options.
I hope that this feature will find some use in various so-called live
disks or to provide a more user-friendly interface for configuring the
system kernel than plain editing of a menuentry command line.
There is one change which could seem to break compatibility with
existing scripts; Before changes introduced in this patch, the ‘export’
command accepted environment variables starting with an ASCII hyphen,
since it wasn't an extcmd. Now, it processes command-line options, so an
extra ‘--’ must be added to process hyphen-prefixed variables.
But in reality, any variable names starting with a hyphen can be only
used in a handful of cases, such as setting their value, exporting them
or displaying on the screen using the ‘set’ command. Their values
_cannot_ be even used in essentially all commands, because the
‘$-something’ or ‘${-something}’ syntax is invalid. Therefore, I assume
that this change would not break any existing GRUB scripts.
Jiří Wolker (2):
Exporting variables to upper levels
Docs for the new options of the ‘export’ command
docs/grub.texi | 10 +++++-
grub-core/kern/env.c | 11 ++++--
grub-core/normal/context.c | 70 ++++++++++++++++++++++++++++++--------
include/grub/env.h | 11 +++++-
4 files changed, 84 insertions(+), 18 deletions(-)
--
2.45.3
_______________________________________________
Grub-devel mailing list
Grub-devel@gnu.org
https://lists.gnu.org/mailman/listinfo/grub-devel
