[Libguestfs] [p2v PATCH 3/4] make-disk: replace here-docs with printfs for better indentation

[Richard W.M. Jones]

On Thu, Jan 19, 2023 at 01:14:47PM +0100, Laszlo Ersek wrote:
> Here-documents break the indentation of the script; replace them with the
> "printf" shell utility. (We could use the <<- redirection operator for
> stripping leading TABs from the here-docs, but the script itself does not
> use TABs for indentation, so that would introduce a different kind of
> inconsistency.)
> 
> Because we use a quoted word ('EOF') for our delimiter in the
> here-documents, variables in the here-docs are not expanded; stick with
> that.
> 
> Use a sole '%s\n' format operand with each printf invocation: "[t]he
> /format/ operand shall be reused as often as necessary to satisfy the
> /argument/ operands"
> <https://pubs.opengroup.org/onlinepubs/9699919799/utilities/printf.html>.
> 
> (I've tried to regression-test this with the two latest Ubuntu images:
> ubuntu-18.04, ubuntu-20.04. The former wouldn't build, and the latter only
> booted to a GDM login screen. My build host is RHEL-9.1, so the kiosk is
> not actually expected to work. Any further investigation here is left to
> Ubuntu users.
> 
> The Fedora 37 image works fine, even with the virt-p2v binary coming from
> RHEL-9.1.)
> 
> Signed-off-by: Laszlo Ersek <lersek at redhat.com>
> ---
>  virt-p2v-make-disk.in | 28 ++++++++++++++--------------
>  1 file changed, 14 insertions(+), 14 deletions(-)
> 
> diff --git a/virt-p2v-make-disk.in b/virt-p2v-make-disk.in
> index 44ff0b45ac7a..0bf7f0e0414f 100644
> --- a/virt-p2v-make-disk.in
> +++ b/virt-p2v-make-disk.in
> @@ -170,15 +170,15 @@ xzcat "$virt_p2v_xz_binary" > "$virt_p2v_binary"
>  case "$osversion" in
>      centos-*|fedora-*|rhel-*|scientificlinux-*|oraclelinux-*)
>          depsfile="$datadir/dependencies.redhat"
> -        cat > $tmpdir/p2v.conf <<'EOF'
> -add_drivers+=" usb-storage "
> -EOF
> -        cat > $tmpdir/post-install <<'EOF'
> -#!/bin/bash
> -# Rebuild the initramfs.
> -latest_version="$(cd /lib/modules; ls -1vr | head -1)"
> -dracut -v -f --kver $latest_version
> -EOF
> +        printf '%s\n'                      \
> +            'add_drivers+=" usb-storage "' \
> +            > $tmpdir/p2v.conf
> +        printf '%s\n'                                                \
> +            '#!/bin/bash'                                            \
> +            '# Rebuild the initramfs.'                               \
> +            'latest_version="$(cd /lib/modules; ls -1vr | head -1)"' \
> +            'dracut -v -f --kver $latest_version'                    \
> +            > $tmpdir/post-install
>          # Double quotes because we want $tmpdir to be expanded:
>          extra_args="
>            --selinux-relabel
> @@ -201,11 +201,11 @@ EOF
>          ;;
>      debian-*|ubuntu-*)
>          depsfile="$datadir/dependencies.debian"
> -        cat > $tmpdir/policy-rc.d <<'EOF'
> -#!/bin/sh
> -# Avoid running daemons during the upgrade/installation
> -exit 101
> -EOF
> +        printf '%s\n' \                                               \
> +            '#!/bin/sh'                                               \
> +            '# Avoid running daemons during the upgrade/installation' \
> +            'exit 101'                                                \
> +            > $tmpdir/policy-rc.d
>          chmod +x $tmpdir/policy-rc.d
>          # Double quotes because we want $tmpdir to be expanded:
>          preinstall_args="

Interesting - didn't know this would work ...

$ printf '%s\n' 'abc' 'def' 123
abc
def
123

It seems like it applies the format pattern to every parameter?!

I verified this works both with bash printf and coreutils.

bash info says:

     The FORMAT is reused as necessary to consume all of the ARGUMENTS.
     If the FORMAT requires more ARGUMENTS than are supplied, the extra
     format specifications behave as if a zero value or null string, as
     appropriate, had been supplied.  The return value is zero on
     success, non-zero on failure.

and almost the same text appears in coreutils info.

So there we are.  ACK!

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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