Is there an advantage to using Bash over Perl or Python? [closed]_问答_开发者

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Hey I've been using Linux for a while and thought it was time to finally dive into shell scripting.

The problem is I've failed to find any significant advantage of using Bash over something like Perl or Python. Are there any performance or power differences between the two? I'd figure Python/Perl would be more well suited as far as power and efficiency goes.

Two advantages come to mind:

Simplicity: direct access to all wonderful linux tools wc, ls, cat, grep, sed... etc. Why constantly use python's subprocess module?
I'm increasingly fond of using gnu parallel, with which you can execute your bash scripts in parallel. E.g. from the man page, batch create thumbs of all jpgs in directory in parallel:

ls *.jpg | parallel convert -geometry 120 {} thumb_{}

By the way, I usually have some python calls in my bash scripts (e.g. for plotting). Use whatever is best for the task!

bash isn't a language so much as a command interpreter that's been hacked to death to allow for things that make it look like a scripting language. It's great for the simplest 1-5 line one-off tasks, but things that are dead simple in Perl or Python like array manipulation are horribly ugly in bash. I also find that bash tends not to pass two critical rules of thumb:

The 6-month rule, which says you should be able to easily discern the purpose and basic mechanics of a script you wrote but haven't looked at in 6 months.
The 'WTF per minute' rule. Everyone has their limit, and mine is pretty small. Once I get to 3 WTFs/min, I'm looking elsewhere.

As for 'shelling out' in scripting languages like Perl and Python, I find that I almost never need to do this, fwiw (disclaimer: I code almost 100% in Python). The Python os and shutil modules have most of what I need most of the time, and there are built-in modules for handling tarfiles, gzip files, zip files, etc. There's a glob module, an fnmatch module... there's a lot of stuff there. If you come across something you need to parallelize, then indent your code a level, put it in a 'run()' method, put that in a class that extends either threading.Thread or multiprocessing.Process, instantiate as many of those as you want, calling 'start()' on each one. Less than 5 minutes to get parallel execution generally.

Best of luck. Hope this helps.

Perl scripts are usually (if not 100% of the times) faster than bash.

A discussion on that: Perl vs Bash

The advantage is that it's right there. Unless you use Python (or Perl) as your shell, writing a script to do a simple loop is a bunch of extra work.

For short, simple scripts that call other programs, I'll use Bash. If I want to keep the output, odds are good that I'll trade up to Python.

For example:

for file in *; do process $file ; done

where process is a program I want to run on each file, or...

while true; do program_with_a_tendency_to_fail ; done

Doing either of those in Python or Perl is overkill.

For actually writing a program that I expect to maintain and use over time, Bash is rarely the right tool for the job. Particularly since most modern Unices come with both Perl and Python.

The most important advantage of POSIX shell scripts over Python or Perl scripts is that a POSIX shell is available on virtually every Unix machine. (There are also a few tasks shell scripts happen to be slightly more convenient for, but that's not a major issue.) If the portability is not an issue for you, I don't see much need to learn shell scripting.

For big projects use a language like Perl.

There are a few things you can only do in bash (for example, alter the calling environment (when a script is sourced rather than run). Also, shell scripting is commonplace. It is worthwhile to learn the basics and learn your way around the available docs.

Plus there are times when knowing a shell well can save your bacon (on a fork-bombed system where you can't start any new processes, or if /usr/bin and or /usr/local/bin fail to mount).

If you want to execute programs installed on the machine, nothing beats bash. You can always make a system call from Perl or Python, but I find it to be a hassle to read return values, etc.

And since you know it will work pretty much anywhere throughout all of of time...

The advantage of shell scripting is that it's globally present on *ix boxes, and has a relatively stable core set of features you can rely on to run everywhere. With Perl and Python you have to worry about whether they're available and if so what version, as there have been significant syntactical incompatibilities throughout their lifespans. (Especially if you include Python 3 and Perl 6.)

The disadvantage of shell scripting is everything else. Shell scripting languages are typically lacking in expressiveness, functionality and performance. And hacking command lines together from strings in a language without strong string processing features and libraries, to ensure the escaping is correct, invites security problems. Unless there's a compelling compatibility reason you need to go with shell, I would personally plump for a scripting language every time.