Standard cmd line separation for option-arguments

Question

Is there a standard for how command-line arguments are passed, or does this differ from program to program? For example, here are a few examples:

1. $ script.py -a 2
2. $ script.py -a=2
3. $ script.py a=2
4. $ script.py --all 2
5. $ script.py --all=2

Answer 1

If you use argparse, you will find support for most of the above options. For example:

# test.py
import argparse
parser = argparse.ArgumentParser(description='Dedupe library.')
parser.add_argument( '-a', '--all', nargs='+', type = int, help='(Optional) Enter one or more Master IDs.')

To run:

df$ python test.py -a 2
# {'all': [2]}
df$ python test.py -a=2
# {'all': [2]}
df$ python test.py a=2
# test.py: error: unrecognized arguments: a=2
$ python test.py --all 2
# {'all': [2]}
$ python test.py --all=2
# {'all': [2]}

As you can see, all are supported except the form of script.py a=2