Regex for parsing a shell command like strings

Question

I am trying to parse strings that look like shell commands. The general structure of these command is the following:

command value -arg1name arg1val -arg2name arg2val ... -argMname argMval

Here is an example,

abc cmdh1521 -x 123 -y sadg -zzz 563sd

I am using the Python re module to parse, search and group strings so that I get an output like this,

(command, value, ((-arg1name, arg1val), (arg2name, arg2val), ... (argMname, argMval))

I tried the following set of commands, but my output is not what I want it to be.

import re
cmd = "abc cmdh1521 -x 123 -y sadg -zzz 563sd"
_parser = r"^([a-z]+)\s{1}(\S*)((\s+\-[a-z]+\s{1}\S+)*)"
out = re.search(_parser, cmd)
print out.groups()

Here is the output I get

('abc', 'cmdh1521', ' -x 123 -y sadg -zzz 563sd', ' -zzz 563sd')

What am I doing wrong?

I can easily implement a non-regex solution, but I would like to know if there is a regex that can give me the kind of parsing I want?

Rahul · Accepted Answer · 2016-02-26 09:30:51Z

2

In this case you will have to use positive lookbehind regex as shown below:

(?<=-)(\w+) ([\w\d]+)

Description and example is at: Demo

answered Feb 26, 2016 at 9:30

Rahul

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Avinash Raj · Accepted Answer · 2016-02-26 09:58:24Z

2

Then again split according to the space exists before -

>>> s = ('abc', 'cmdh1521', ' -x 123 -y sadg -zzz 563sd', ' -zzz 563sd')
>>> h = []
>>> for i in s:
    if '-' not in i:
        h.append(i)
    else:
        for j in re.split(r'\s+(?=-)', i):
            if j:
                h.append(j)


>>> h
['abc', 'cmdh1521', '-x 123', '-y sadg', '-zzz 563sd', '-zzz 563sd']
>>>

or

>>> cmd = "abc cmdh1521 -x 123 -y sadg -zzz 563sd"
>>> import re
>>> re.findall(r'^(\S+)\s+(\S+)|(-\S+\s+\S+)', cmd)
[('abc', 'cmdh1521', ''), ('', '', '-x 123'), ('', '', '-y sadg'), ('', '', '-zzz 563sd')]
>>> [j for i in z for j in i if j ]
['abc', 'cmdh1521', '-x 123', '-y sadg', '-zzz 563sd']
>>>

edited Feb 26, 2016 at 9:58

answered Feb 26, 2016 at 9:26

Avinash Raj

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1 Comment

siva82kb Over a year ago

Can I get the kind of parsing I want without having to resort to manually segmenting these individual strings like you have done?

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