Re: GRUB 2.00 conditional structures (statements) syntax

[Andrey Borzenkov]

В Tue, 15 Oct 2013 12:20:16 +0200
address@hidden пишет:

> Dear all, 
> 
> unfortunately i was not able to find any documentation on usage of 
> conditional statements in grub configuration files.
> 
> According to the “GNU GRUB Manual 2.00~rc1” found on http://www.gnu.org/ the 
> words 'if', 'fi', 'case', 'esac', 'in' and so on are reserved.
> Furthermore the scripting language is referred to as “Shell-like”.
> 
> Simple “if [ $condition ]; then #dosomething; fi”-statements are not 
> problematic.
> But I wasn't able to find a functional syntax for the case-statements.
> 

grub does not support "case" statement, at least as of now.

> To make it short: I would like to compare strings in the grub cli.
> 
> Is there any more or less exhaustive documentation about the syntax or am I 
> just too dumb to use google?
> 

What part is unclear?

"case" can in almost all cases be replaced with "if". Actually, perl
never had "case" too. That said, if someone implements it, I guess it
will be accepted.

To compare patters you can use regexp command. Current trunk contains a
bit more complete list of available commands. 

> The most recent version I used to test stuff was the 2.00 that comes shipped 
> with arch linux.
> 
> 
> What I'm trying to do:
> 
> I want to implement a grub configuration file that automatically generates 
> menu entries.
> 
> For en example: 
> The following procedure should create entries for (small) files to be loaded 
> with memdisk ( from the syslinux project).
> /boot/memsik is our kernel.
> Our file is the initrd.
> We assume that the files can be PREFIX_*.* or just *.* or README*.
> (e.g. README || FLOPPY_dellbiosupdate.img || freedos.img)
> The README*-files should not be processed.
> For files with a prefix, the prefix should be appended as a kernel-parameter.
> For files without there are no parameters to append.
> 
> I supposed that this would be “shell-like” (file=$img):
> 
> [code source=”/boot/grub/grub.cfg”]
> . ..
> insmod ext2
> insmod regexp
> . ..
> set pathtoimages=”/boot/images”
> . ..
> for img in ${pathtoimages}/*; do
>   set appendstr=””
>   ...
>   case ${img} in
>     */README*)  continue  ;;
>     */FLOPPY_*) set appendstr=${appendstr} floppy ;;
>       …
>   esac
>   menuentry “MEMDISK - $img” “$img” “$appendstr” {
>     linux16 /boot/memdisk ${3}
>     initrd16 ${2}
>   }
> done
> . ..
> [/code]
> 
> I also tried to use other quoting notations with no success.
> Futhermore I also tried “if [[ ${img} == */FLOPPY_* ]]; ...”.
> 
> 
> 
> Thank you very much in advance!
> 
> 
> 
> With kind regards, 
>     Sasha B.
> 
> 
> 
> P.S.: Sorry if something's misspelled, English isn't my native tongue.
> 
> 
> 
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