Libguestfs - Jun 2021 - [libnbd PATCH 03/20] nbdsh: Check for python-exec2c installations

Platforms that utilise python-exec [0] wrapper scripts (mainly Gentoo) utilise
basenames of python scripts and executables to decide which python
implementation to use for running that particular command.  That makes the nbdsh
"hack" in sh/nbdsh.in not work, even if 'exec -a' is supported
by sh.

Signed-off-by: Martin Kletzander <mkletzan at redhat.com>
---
 sh/nbdsh.in | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/sh/nbdsh.in b/sh/nbdsh.in
index d10f0c1b6b26..333c2d5f8b96 100644
--- a/sh/nbdsh.in
+++ b/sh/nbdsh.in
@@ -19,7 +19,8 @@
 
 # Test if /bin/sh supports exec -a option (only supported in bash 4.2
 # and above, and not part of POSIX).
-if /bin/sh -c 'exec -a test true' 2>/dev/null; then
+if /bin/sh -c 'exec -a test true' 2>/dev/null && \
+        test $(readlink $(which @PYTHON@)) != python-exec2c; then
     exec -a nbdsh @PYTHON@ -mnbd "$@"
 else
     exec          @PYTHON@ -mnbd "$@"
-- 
2.31.1

On Tue, Jun 08, 2021 at 09:53:44AM +0200, Martin Kletzander
wrote:
> Platforms that utilise python-exec [0] wrapper scripts (mainly Gentoo)
utilise
Did you mean "[0]" to reference a URL?
> basenames of python scripts and executables to decide which python
> implementation to use for running that particular command.  That
> makes the nbdsh "hack" in sh/nbdsh.in not work, even if 'exec
-a' is
> supported by sh.
It's annoying that we have to work around Gentoo here by adding a
dependency on coreutils.  I suppose FreeBSD does have readlink(1).
But my feeling is that the Gentoo script is broken if it cannot cope
with an unexpected basename.

Would a configure-time test be better here?  It seems like it would
have less chance of breaking on the end-user machine (I know that on
Gentoo, "end-user" is a distinction without a difference but it would
make nbdsh more robust on non-Gentoo).  Also it would mean the package
didn't need to depend on coreutils.

Rich.
> Signed-off-by: Martin Kletzander <mkletzan at redhat.com>
> ---
>  sh/nbdsh.in | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/sh/nbdsh.in b/sh/nbdsh.in
> index d10f0c1b6b26..333c2d5f8b96 100644
> --- a/sh/nbdsh.in
> +++ b/sh/nbdsh.in
> @@ -19,7 +19,8 @@
>  
>  # Test if /bin/sh supports exec -a option (only supported in bash 4.2
>  # and above, and not part of POSIX).
> -if /bin/sh -c 'exec -a test true' 2>/dev/null; then
> +if /bin/sh -c 'exec -a test true' 2>/dev/null && \
> +        test $(readlink $(which @PYTHON@)) != python-exec2c; then
>      exec -a nbdsh @PYTHON@ -mnbd "$@"
>  else
>      exec          @PYTHON@ -mnbd "$@"
> -- 
> 2.31.1
> 
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-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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