Find the path of a shell command

[Jon Ribbens]

On 2022-10-12, Jon Ribbens <jon+usenet at unequivocal.eu> wrote:
> 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'

Actually if I'm mentioning shutil I should probably mention
shutil.rmtree() as well, which does the same as 'rm -r', without
needing to find or run any other executables.