Find the path of a shell command

[Jon Ribbens]

On 2022-10-12, Paulo da Silva <p_d_a_s_i_l_v_a_ns at nonetnoaddress.pt> wrote:
> Às 19:14 de 12/10/22, Jon Ribbens escreveu:
>> On 2022-10-12, Paulo da Silva <p_d_a_s_i_l_v_a_ns at nonetnoaddress.pt> wrote:
>>> Às 05:00 de 12/10/22, Paulo da Silva escreveu:
>>>> Hi!
>>>>
>>>> The simple question: How do I find the full path of a shell command
>>>> (linux), i.e. how do I obtain the corresponding of, for example,
>>>> "type rm" in command line?
>>>>
>>>> The reason:
>>>> I have python program that launches a detached rm. It works pretty well
>>>> until it is invoked by cron! I suspect that for cron we need to specify
>>>> the full path.
>>>> Of course I can hardcode /usr/bin/rm. But, is rm always in /usr/bin?
>>>> What about other commands?
>>>>
>>> Thank you all who have responded so far.
>>> I think that the the suggestion of searching the PATH env seems the best.
>>> Another thing that I thought of is that of the 'which', but, to avoid
>>> the mentioned recurrent problem of not knowing where 'which' is I would
>>> use 'type' instead. 'type' is a bash (sh?) command.
>> 
>> If you're using subprocess.run / subprocess.Popen then the computer is
>> *already* searching PATH for you.
> Yes, and it works out of cron.
>> Your problem must be that your cron
>> job is being run without PATH being set, perhaps you just need to edit
>> your crontab to set PATH to something sensible.
> I could do that, but I am using /etc/cron.* for convenience.
>
>> Or just hard-code your
>> program to run '/bin/rm' explicitly, which should always work (unless
>> you're on Windows, of course!)
> It can also be in /bin, at least.

I assume you mean /usr/bin. But it doesn't matter. As already
discussed, even if 'rm' is in /usr/bin, it will be in /bin as well
(or /usr/bin and /bin will be symlinks to the same place).

> A short idea is to just check /bin/rm and /usr/bin/rm, but I prefer 
> searching thru PATH env. It only needs to do that once.

I cannot think of any situation in which that will help you. But if for
some reason you really want to do that, you can use the shutil.which()
function from the standard library:

    >>> import shutil
    >>> shutil.which('rm')
    '/usr/bin/rm'