From: Alec Ross <alec@...>
Date: 2010-12-22T07:45:18+09:00
Subject: Re: Someone explain to me the logic behind ARGV[0]

In message <4C1A26450D42B303@smtp205.alice.it>, Stefano Crocco 
<stefano.crocco@alice.it> writes
>On Saturday 18 December 2010 19:12:57 Kaye Ng wrote:
...

>> For example there's a code
>> lines = File.readlines(ARGV[0])
>> Why do i need the [0]?
>>
>> I have another program, testingargv.rb with this code
>> puts ARGV.join('-')
>> (no [0] parameter)
>> if i type in the command prompt, testingargv.rb test 123
>> the result is test-123
>>
>> i don't understand the logic behind [0] in
>> lines = File.readlines(ARGV[0])
>>
>> thanks guys!
>
>ARGV is an array. Calling ARGV[0] returns the first argument of the array,

...

This naming and usage stems back to the C programming language. There, 
argv is the conventional name for any command line arguments to the 
program, and it denotes an array of c-style strings.  Elements of an 
array in C are accessed by a (0-based) index.  Hence argv[0] gets the 
first argument value, argv[1] the second, and so on.

HTH,

Alec
-- 
Alec Ross