UNIX for Dummies Questions & Answers

Hi all...

Not sure where to put this so I put it here...

All comments welcome...

1) Is the Python language now considered a part of the *NIX transient command structure much like Perl, (and awk)?

2) If so which OSes now have it as part of a "default" install - NOT an extra to be downloaded from repositories at a later date.

3) Also, if so, which version(s) does your *NIX, Linux, MacOS, etc, etc have?

(Note:- I already know that Debian, PCLinuxOS and MacOS does.)

TIA...

Bazza...

This question sounds like "are cars usually red"? There are without a doubt a lot of red cars, but this means nothing if you what to know if this specific car is red or not. What you are interested in is, if the software is installed on the specific system you want to run some script on. If some other systems have it or not doesn't matter.

What "UNIX" constitutes is defined in the "Single Unix Specification", the "POSIX" specification and similar documents. Today a UNIX system is not required to use some specific (AT&T-) code, but to react in a (thusly) specified way. "awk" is part of this specification, "perl" is not. And neither is "python". If you want to write portable scripts you should consider using the POSIX shell (which resembles mostly the ksh88).

The system i use most - AIX - definitely doesn't have it in the default install and for AIX - as well as any other systems i use - the term "default install" is meaningless. When i install a production system i use a carefully crafted absolute-minimum-image ("golden image") and install of this what is needed. What can be expected because of the POSIX specification is there (all tools listed as "mandatory"), but not more. Everything installed will have to be maintained, can break, etc. and if you have thousands of systems in a data center (quite the common case) you want to keep the things which can break at an absolute minimum.

I hope this helps.

bakunin

Hi bakunin...

Thanks a lot for that, I will research the POSIX spec' in as much depth as the online WWW documentation allows.

I had no idea that the transient command structure was dynamic and that there is a minimal requirement.

I assumed, (bad move on my part), Perl was, as all the, (_consumer_), Linux installs I have seen have it.

Thanks again...

Every command is a single executable. When you type "ls" you invoke "/usr/bin/ls", which is a program in its own right, quite as any other program. Now there might be a package "basic.commands", which bundles "ls" with other, similarily ubiquitous commands, but that doesn't have to be so. You could remove "/usr/bin/ls" from a system with no other consequence than not being able to list directories/files.

Now, there is a list of programs ("commands"), which is described in the POSIX documents as "mandatory". That means, if a systems calls itself "UNIX" it can be expected to have these programs. "ls" is part of this list, as is "awk", "sed", "sh", etc.. These commands should be installed wether or not they are actually used in a script running on this system. The same goes for libraries, interfaces, system calls, and similar functions of the system. All these are described in the POSIX documents. For the example "ls" this would mean there is a description about which commandlne options it has to understand and what exactly these options will make "ls" do when invoked.

Everything else is installed on top of that, but it is not "UNIX", just very common. That goes for "perl" as well as "gzip" and "ssh" and whatnot. These are quite common tools, but not "part of the UNIX system". It was once quite common to have these annoying nodding sausage dogs in the back of a car, but just because these are (or were) quite common doesn't mean they were "part of the system 'automobile'", like the steering wheel or the brake.

I hope this helps.

bakunin

Hi bakunin...

Thanks a lot.
All taken in and researching further...

The scientific and high performance computing distributions generally offer Python as prt of the standard install. Search the distrowatch.com site for examples.
Mind you, these are distributions that have a custom made install script that happens to include Python and some Python libraries. There is obviously nothing stopping you from writing a script of your own on top of a bare bones Linux installation.
The BSD ecosystem generally does not have Python upon installation.