From: dblack@...
Date: 2007-01-04T05:17:46+09:00
Subject: Re: Delete line from file

Hi --

On Thu, 4 Jan 2007, William James wrote:

>
> dblack@wobblini.net wrote:
>> Hi --
>>
>> On Wed, 3 Jan 2007, William James wrote:
>>
>>>
>>> Jules wrote:
>>>> Hi,
>>>>
>>>> Given a line number, what is the best way to delete this line from a
>>>> file?
>>>>
>>>> And given an array of line numbers, what is the best way to delete
>>>> these lines from a file?
>>>>
>>>> Thanks,
>>>>
>>>> Jules
>>>
>>> lines = IO.readlines('junk1')
>>> [1,3,5].each{|n| lines.slice!(n) }
>>
>> That's going to have a side-effect problem:
>>
>> irb(main):004:0> a = %w{ a b c d e f }
>> => ["a", "b", "c", "d", "e", "f"]
>> irb(main):005:0> [1,3,5].each {|e| a.slice!(e) }
>> => [1, 3, 5]
>> irb(main):006:0> a
>> => ["a", "c", "d", "f"]
>
> True.
>
> a = %w(zero one two three four five)
> [1,3,5].each{|i| a[i]=nil}
> a.compact!

That's OK if you don't have any nils in the array you want to keep.
Reversing the index list should be pretty glitch-proof, I think.


David

-- 
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