calibre-uninstall doesn't run on Ubuntu 20.04

[Junaid Ahmed]

Calibre is installed using the command as per stated in official website-

"sudo -v && wget -nv -O- https://download.calibre-ebook.com/linux-installer.sh | sudo sh /dev/stdin"

The "calibre-uninstall" file successfully generates in /bin
But running "sudo calibre-uninstall" returns error- "No such file or directory".
Opening the "calibre-uninstall" file with text-editor reveals that the file lists the address of python in "/usr/bin/python". There is no longer a "python" file in "/usr/bin" on a freshly installed Ubuntu 20.04, it has been replaced by the file "python3".
Editing the "calibre-uninstall" file to rename the package as "python3" works and uninstall process completes without any error.
Requesting appropriate change(s).

[Eli Schwartz (eschwartz)]

The linux-installer.py script has already been switched for Ubuntu's
convenience to be a shellscript that repeatedly tries to find various
interpreters. So that's one option.

Maybe, however, it would be better to make calibre.linux:PostInstall
accept another argument, which linux-installer.py would populate as

pi.extend(['--python-cmd', sys.executable])

This would ensure that whichever python command was used when
linux-installer.sh probed for a suitable $PYTHON to run its integrated
heredoc, was also embedded into the calibre-uninstall program.

setup/install.py could make opts.python_cmd default to sys.executable
for from-source builds, and for the case where someone uses an isolated
install of the binary build, then later runs calibre_postinstall, they
can either manually specify it or let it assume /usr/bin/python.

[Kovid Goyal (kovid)]

@Eli: Not sure that is the best approach. What if sys.executable points
to something like /usr/bin/python3.7 then it will break if python is
upgraded. Might be better to point to the installed path of
calibre-debug which can run python scripts.

[Kovid Goyal (kovid)]

The problem with that is we dont know where calibre-debug will be
installed, so the best we can do is hope it is in the path.

Maybe best to just wrap the uninstaller is a .sh like we do for the
installer, and send Canonical the bill for my time wasted.

[Eli Schwartz (eschwartz)]

Apparently in commit ddca079000ffd03611d19c5dfe29341b9c1c6e2e it was
changed from using sys.executable in the postinstall script itself due
to bug 1283154

Which I suppose is... understandable as it seemed to be the
bin/calibre_postinstall program? calibre-debug itself should work, I
suppose, as long as it's the right one...

Use of calibre-debug as a script interpreter is indeed a good point.

[Eli Schwartz (eschwartz)]

Nah, sure you know where the calibre-debug program is installed. It's
used to create symlinks on frozen builds (this whole codepath is only
run when sys.frozen_path exists, so getattr seems unneeded):

tgt = os.path.join(getattr(sys, 'frozen_path'), exe)
self.info('\tSymlinking %s to %s'%(tgt, dest))

So calibre-debug on frozen builds can be guaranteed to be at

os.path.join(sys.frozen_path, 'calibre-debug')

For non-frozen builds opts.bindir should have this passed along from
setup/install.py

[Kovid Goyal (kovid)]

Still, I think I prefer to have the uninstaller independent of the rest
of calibre, in case of corrupted installs, or similar.

[Eli Schwartz (eschwartz)]

I've experimented a bit with the idea, here, in case you're interested:

https://github.com/eli-schwartz/calibre/commit/fabc34b8cef782849d2e14e7d5f73dfe5b93b07c

[Kovid Goyal (kovid)]

Fixed in branch master. The fix will be in the next release. calibre is usually released every alternate Friday.

 status fixreleased

[Eli Schwartz (eschwartz)]

Note that because shell scripts are *wonderful*, you cannot rely on $0
being the path to the calibre-uninstall script (programs are freely
permitted to define their own argv0), and in some cases it won't be
deleted properly (although everything else will be).

e.g. one way to *accidentally* trigger this is with

bash calibre-uninstall

$0 will be 'calibre-uninstall', bash detects the program on $PATH, but
it's not relative to ./ and you cannot trace it back to the original
source file, so the uninstaller doesn't get detected as existing.

The bash-specific equivalent of `__file__` is ${BASH_SOURCE[0]} which
has nothing to do with argv0 and does, in fact, explicitly refer to the
filename of the file which is currently being parsed, but /bin/sh has
*no* way of detecting this. None. Period. It cannot be done.

(In order to break BASH_SOURCE you need to do something like:
`cat /usr/bin/calibre-uninstall | bash`, which would break python
`__file__` too.)

It's *probably* okay to say "if you find yourself invoking the
calibre-uninstall program in some way that lies about $0, you deserve to
not have it uninstalled with the rest".

Just thought you might be interested in adding to the list of
frustrations to bill Canonical for. :)

[Kovid Goyal (kovid)]

Yeah, I know, but since there is no a-priori reason to run
calibre-uninstall as anything but calibre-uninstall, I am ok with
it being a little fragile.

[Patrice (patrice-hardouin)]

The command sudo -v && sudo calibre-uninstall && wget -nv -O- https://download.calibre-ebook.com/linux-installer.sh | sudo sh /dev/stdin version=3.48.0 doesn't work under ubuntu 20.04

Also, a code response 404 appear with all old versions.

[Patrice (patrice-hardouin)]

The fix isn't released in 5.4.2