is a wildcarded bbappend file name valid without a "_"?

is a wildcarded bbappend file name valid without a "_"?

[Robert P. J. Day]

  wasn't sure where to ask this but since i read it in the bitbake
manual, i figured, let's ask docs.

  regarding using wildcarding in bbappend file names, the bitbake
manual insists:

"In the most general case, you could name the append file something as
simple as busybox_%.bbappend to be entirely version independent."

  ok, fair enough, that appears to imply that even in the most general
form of wildcarding, you would have the underscore just before the "%"
wildcard character.

  but i've seen a number of examples where even the underscore is
omitted, such as in this search under the meta-security layer, where
the final line shows that the underscore is missing from the filename:

$ find . -name "linux-yocto*bbappend"
./recipes-kernel/linux/linux-yocto-rt_%.bbappend
./recipes-kernel/linux/linux-yocto_%.bbappend
./meta-tpm/recipes-kernel/linux/linux-yocto-rt_%.bbappend
./meta-tpm/recipes-kernel/linux/linux-yocto_%.bbappend
./meta-integrity/recipes-kernel/linux/linux-yocto%.bbappend
$

  so this is clearly legal. should it be mentioned as being legal? or
discouraged? the bitbake manual certainly doesn't explain that this is
a valid form of wildcarding. should it?

rday

Re: [docs] is a wildcarded bbappend file name valid without a "_"?

[Quentin Schulz]

Hi Robert,

On 1/7/26 1:51 PM, Robert P. J. Day via lists.yoctoproject.org wrote:
> 
>    wasn't sure where to ask this but since i read it in the bitbake
> manual, i figured, let's ask docs.
> 
>    regarding using wildcarding in bbappend file names, the bitbake
> manual insists:
> 
> "In the most general case, you could name the append file something as
> simple as busybox_%.bbappend to be entirely version independent."
> 
>    ok, fair enough, that appears to imply that even in the most general
> form of wildcarding, you would have the underscore just before the "%"
> wildcard character.
> 
>    but i've seen a number of examples where even the underscore is
> omitted, such as in this search under the meta-security layer, where
> the final line shows that the underscore is missing from the filename:
> 
> $ find . -name "linux-yocto*bbappend"
> ./recipes-kernel/linux/linux-yocto-rt_%.bbappend
> ./recipes-kernel/linux/linux-yocto_%.bbappend
> ./meta-tpm/recipes-kernel/linux/linux-yocto-rt_%.bbappend
> ./meta-tpm/recipes-kernel/linux/linux-yocto_%.bbappend
> ./meta-integrity/recipes-kernel/linux/linux-yocto%.bbappend
> $
> 
>    so this is clearly legal. should it be mentioned as being legal? or

It's been used for a while (had this in meta-rockchip for years for 
u-boot, but that was not what we were supposed to do), so I would be for 
documenting it.

I would add a note about really thinking twice before doing this because 
it can match more than one thinks and impact third party layers which 
asked for nothing. E.g. the u-boot%.bbappend we used to have in 
meta-rockchip used to modify my u-boot-cherry-es recipe if I remember 
correctly, which is typically not something you want to do. In the 
example above, linux-yocto% is probably safe enough as I am not sure 
people would name their own kernel recipe linux-yocto-something. But 
linux% would be a no-no in my book.

Cheers,
Quentin

Re: [docs] is a wildcarded bbappend file name valid without a "_"?

[Richard Purdie]

On Wed, 2026-01-07 at 14:40 +0100, Quentin Schulz via lists.yoctoproject.org wrote:
> Hi Robert,
> 
> On 1/7/26 1:51 PM, Robert P. J. Day via lists.yoctoproject.org wrote:
> > 
> >    wasn't sure where to ask this but since i read it in the bitbake
> > manual, i figured, let's ask docs.
> > 
> >    regarding using wildcarding in bbappend file names, the bitbake
> > manual insists:
> > 
> > "In the most general case, you could name the append file something as
> > simple as busybox_%.bbappend to be entirely version independent."
> > 
> >    ok, fair enough, that appears to imply that even in the most general
> > form of wildcarding, you would have the underscore just before the "%"
> > wildcard character.
> > 
> >    but i've seen a number of examples where even the underscore is
> > omitted, such as in this search under the meta-security layer, where
> > the final line shows that the underscore is missing from the filename:
> > 
> > $ find . -name "linux-yocto*bbappend"
> > ./recipes-kernel/linux/linux-yocto-rt_%.bbappend
> > ./recipes-kernel/linux/linux-yocto_%.bbappend
> > ./meta-tpm/recipes-kernel/linux/linux-yocto-rt_%.bbappend
> > ./meta-tpm/recipes-kernel/linux/linux-yocto_%.bbappend
> > ./meta-integrity/recipes-kernel/linux/linux-yocto%.bbappend
> > $
> > 
> >    so this is clearly legal. should it be mentioned as being legal? or
> 
> It's been used for a while (had this in meta-rockchip for years for 
> u-boot, but that was not what we were supposed to do), so I would be for 
> documenting it.
> 
> I would add a note about really thinking twice before doing this because 
> it can match more than one thinks and impact third party layers which
> asked for nothing. E.g. the u-boot%.bbappend we used to have in 
> meta-rockchip used to modify my u-boot-cherry-es recipe if I remember
> correctly, which is typically not something you want to do. In the 
> example above, linux-yocto% is probably safe enough as I am not sure 
> people would name their own kernel recipe linux-yocto-something. But 
> linux% would be a no-no in my book.

Right, the _ is highly recommended as an anchor but you don't have to
do that. So it isn't "the most general case" as that could be
"a%.bbappend" or something but we don't really want to encourage it.

Cheers,

Richard