On Thu, May 31, 2018 at 9:34 AM, Cameron Simpson <c...@cskk.id.au> wrote:
> On 30May2018 21:29, MRAB <pyt...@mrabarnett.plus.com> wrote:
>>
>> On 2018-05-30 21:01, Paul St George wrote:
>>>
>>> Is this equivalent?
>>> p = subprocess.Popen('display', + imagepath)
>>>
>> p = subprocess.Popen(['display', imagepath])
>>
>>> so
>>>
>>> p = subprocess.Popen('display', 'test.png')
>>>
>> p = subprocess.Popen(['display', 'test.png'])
>>
>> Remembering to provide the full paths (unless it's/they're on the system's
>> search path).
>
>
> Personally, I am generally against the "use a full path" advice.
>
> Using a full path to the executable is (a) nonportable because executables
> may be in different places on different systems and (b) obstructive to the
> user, because they may have built or installed their own version of the app
> for specific purposes, such as the vendor provided version being out of
> date.
>
> For example, Paul's problem might also be addressable by writing his own
> "display" shell script invoking the tool of his choice. Like Python, the
> executable command name is a dynamic lookup!
>
> IMO it is the programme caller's task to provide the execution environment,
> and the programme should expect $PATH (UNIX execution search path) to be
> suitable already.
>
> Every hardwired path is a maintenance and fragility nightmare.
Bless you, it all depends! [1]
A hardwired path is safe against someone externally messing with your
script. But a pathless name allows you to make use of
externally-configured $PATH. Sometimes you want the safety; sometimes
you want the flexibility.
Using just the name is very similar to typing the command at the
shell, but it's not identical to that either; shell aliases can mean
that typing "grep foo bar" is not the same as "`which grep` foo bar".
So it's that bit harder to explain, and you HAVE to want the behaviour
that it gives.
Make an intelligent decision as to whether you want a hard-coded path
or just a name.
ChrisA
[1] I'm on the wrong mailing list to expect everyone to recognize that
line. It's from "The Mikado" by Gilbert & Sullivan.
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