[Libguestfs] [PATCH 3/3] Add 'virt-rescue' command.

[Jim Meyering]

Richard W.M. Jones wrote:
...
> Subject: [PATCH 3/3] Add 'virt-rescue' command.
>
> This command runs a "rescue appliance" against a virtual machine
> or disk image.  This is useful for making ad-hoc interactive
...
> diff --git a/rescue/Makefile.am b/rescue/Makefile.am
...
> +if HAVE_RESCUE
> +
> +man_MANS = virt-rescue.1

I have a vague memory that recent automake generates
better rules if you spell the above like this:

  dist_man1_MANS = virt-rescue.1

> +noinst_DATA = @top_builddir@/html/virt-rescue.1.html

IMHO, it's better to avoid automake's obsolescent @VAR@ notation.
Instead, use $(VAR).  There's even a syntax-check rule for this,
but it's currently disabled.

> +virt-rescue.1: virt-rescue.pl
> +	$(POD2MAN) \
> +	  --section 1 \
> +	  -c "Virtualization Support" \
> +	  --release "$(PACKAGE_NAME)-$(PACKAGE_VERSION)" \
> +	  $< > $@

Don't redirect directly to $@, in case the command fails
without removing the incomplete result.  This idiom ensures
that it is updated atomically:

   	  $< > $@-t && mv $@-t $@

> + at top_builddir@/html/virt-rescue.1.html: virt-rescue.pl
> +	mkdir -p @top_builddir@/html
> +	cd @top_builddir@ && pod2html \
> +	  --css 'pod.css' \
> +	  --title 'virt-rescue, run a rescue shell on a virtual machine' \
> +	  --htmldir html \
> +	  --outfile html/virt-rescue.1.html \
> +	  rescue/$<
> +
> +install-data-hook:
> +	mkdir -p $(DESTDIR)$(bindir)
> +	install -m 0755 virt-rescue.pl $(DESTDIR)$(bindir)/virt-rescue
> +
> +endif



> diff --git a/rescue/run-rescue-locally b/rescue/run-rescue-locally
...
> +my $path = $0;
> +
> +# Follow symlinks until we get to the real file
> +while(-l $path) {
> +    my $link = readlink($path);

You'll want to handle the case in which readlink fails
and returns "undef".

> +    if(File::Spec->file_name_is_absolute($link)) {
> +        $path = $link;
> +    } else {
> +        $path = File::Spec->catfile(dirname($path), $link);
> +    }