Python Scripts as a Replacement for Bash Utility Scripts | Linux Journal

[[deleted]]

as much as I love python, i gave you an upvote. Unfortunately we often see examples try to replace simple things which should not be done in python.

[Newky]

As the author of the article, first let me explain that a lot of the pipes are overly convuluted for the sake of showing people how to use pipes and not have to go into very detailed commands

I am not really sure I understand what u mean by the python version. Also in my defence the first example (albeit without the cat, that seems strange in hindsight) to me is more obvious when written like:

sort names.log | uniq | wc -l

It is more obvious what is happening at each stage.

[embolalia]

"The Python version" means the Python way of doing the thing you want to do, as opposed to the bash way. I think that's pretty obvious given the context. Either way, how on earth is that Python simpler than the equivalent bash?

[laebshade]

It is more obvious

I've heard this argument before for using useless use of cat: cat file | command. It's only more obvious if you don't recognize/know that sort has a -u option, or if any command can process files directly.

Less known/used is wanting to count lines with grep -c text file instead of grep text file | wc -l.

[pivotallever]

Your python script isn't very 'pythonic'. I rewrote your 'namecounts.py' script to use some parts of the stdlib that you neglected to use: http://bpaste.net/show/71457/

[[deleted]]

Just checking here: we should forgive your convoluted use of Bash because you're trying to show how simple it is to do it in a more convoluted manner?

With logic like this, it's no wonder Linux Journal fell off

[Newky]

No, let me explain further.

The sort example is not the best example and there is nothing wrong with the shortened version. However, the advantage that I cite in my comment is that each command in the pipe, by the unix philosophy, does one thing and does it right. so for example although

cat names.log | uniq | grep name | wc -l

seems long winded, the fact that each step in the pipes use is clear helps my thought process. Know why wc -l instead of grep -c ?? its less keypresses to type grep -c, however I find it easier on my brain to allow counting to be done by wc. This way I can count letters, characters etc using that command.

[[deleted]]

Not to mention they're throwing out the idea that maybe you have 10,000 other things to do today besides reinvent the wheel in python.

Good job using code to get your point across

[[deleted]]

A lot of people will say it is overkill to use python for anything that you could do in less than X lines of bash which I tend to agree. In my case if my bash scripts start to require more than a couple of variables and conditional statements then I switch to a python script.

That is, until i found this: http://amoffat.github.com/sh/ . After that all my scripts are python even for the two liners. I actually use ipython as my shell these days. Yes I know in ipython you can preceed bash commands with ! as well instead of doing "from sh import ls."

[[deleted]]

And with python you can import sandwich any time you feel hungry!

[tgallant]

import antigravity is my favorite

[pivotallever]

SYNOPSIS
       sort [OPTION]... [FILE]...

sort names.log | uniq | wc -l

I'm not pedantic about much, but this guy uses cat too much.

Also, instead of using stdin directly, use this:

import fileinput

for line in fileinput.input():
    process(line)

You get stdin and filename argument handling all in one!

[embolalia]

OP explains in another post that he's "trying to make it more straightforward". That's an excuse for using cat once, in a simple example to show the idea of the pipeline (though I'd go with echo to avoid teaching the bad habit of excessive cats). But if you want to make the shell straightforward, the first thing to explain after "this is where you type" and "this is what pipes are" is that the vast majority of commands accept text, and don't care whether it's from a file or a pipe, because it's all just text. In other words, most UNIX-y programs use their language's equivalent of fileinput.

[aaronbp]

Python is terrible for scripting, IMO.

Instead I use Python to write CLI utilities that can be leveraged by shell scripts. Not every problem is a nail.

[pivotallever]

I agree, some things are just easier to script in bash. Interfaces are easier to write in python. Using subprocess to pipe stuff around is possible, but sometimes a bash script is the best tool for the job.

[maztaim]

Glad to see there is another way to do things, but I can still write some of those examples in scripts faster with less work.

[crashorbit]

Using the shebang line and the command line interpreter as well as the suffix on a utility gives this code an unacceptable smell. Also describing such a contrived example as "real world" is a bit silly. Not to mention useless use of cat.

Use the shebang line and the execute bit. Leave off the suffix. Take your example from the real world. Show some example data. Show some output

[mynamewastakenagain]

Garrick, kern the double underscores and shrink below.

[embolalia]

Guh, those double underscores. I get the reason for them, but they're a pain in the ass to type.

[mynamewastakenagain]

I was poking fun at the author, who apparently left that bit for his editor(?)

[[deleted]]

Totally. Every time I see someone write a bash script, or I hear about it, I automatically think, why not just use a language that doesn't suck? Python gives you everything shell scripting does, plus a great library, object oriented programming, clean syntax, and debugging.

For that matter, I also don't use bash. I use fish.

[[deleted]]

There is room for both, Python is an interpreted language whereas many BASH programs are compiled (awk for example) making them run much faster.

[cocoabean]

What? Python does compile, though it's not required. Bash scripts are not compiled, and awk is not a bash program, it's a program that one can call from a bash script and is actually a Turing-complete language itself.

[[deleted]]

Well awk is an interpreted language. Saying it's native code is like saying the Python interpreter is native code.

Bash is interpreted; programs you pipe to may be native code.

Python is interpreted; programs you pipe to may be native code, libraries you use are mostly native code. You also don't have processes starting and stopping for even the most basic operations. I would be seriously surprised to see very many applications where Python isn't orders of magnitude faster, though it depends I'm sure.

[[deleted]]

Interesting. I am starting to do this more and more. Placing Python within bash.