Find the path of a shell command

[Paulo da Silva]

Às 22:38 de 12/10/22, Jon Ribbens escreveu:
> 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.
Except that you can't have parallel tasks, at least in an easy way.
Using Popen I just launch rm's and end the script.