From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2009-12-24T02:23:48+09:00
Subject: Re: awk print $4 in ruby

On Wed, Dec 23, 2009 at 6:06 PM, Derek Smith
<derekbellnersmith@yahoo.com> wrote:
> Derek Smith wrote:
>>>>      df -k | ruby -lane 'print $F[3]'
>>>
>>> yes and no.  I prefer it in script form no CLI form.
>>>
>>> dfstr = Array.new
>>> dfstr << %x(df -m)
>>> dfstr.each do |line|
>>>     ?????
>>> end
>>
>> Tried this too:
>>
>> $; = 'Avail'
>> dfstr = %x(df -m)
>> puts dfstr[$;]
>
> I got it using, but ideally would not like to use a file on the FS.
> Any comments welcome! :)
>
> Merry Xmas!
> Thank you!
>
>
> DFSTR = "/tmp/dfstr.out"
> %x(df -m > "#{DFSTR}")
> file = File.open("#{DFSTR}", "r")
> file.each do |ln|
>    ln.chomp
>    fsaray = []
>    fsaray = ln.split
>    puts fsaray[3]
> end

You don't need a file, cause df will return a string with each line
separated by "\n", which the "each" method in string defaults to as a
separator:

irb(main):001:0> s = %x{df -k}
irb(main):002:0> s.each {|line| p line}
"Filesystem           1K-blocks      Used Available Use% Mounted on\n"
"/dev/sda1            147549816  17405644 122649048  13% /\n"
"tmpfs                  1815116         0   1815116   0% /lib/init/rw\n"
"varrun                 1815116       132   1814984   1% /var/run\n"
"varlock                1815116         0   1815116   0% /var/lock\n"
"udev                   1815116      2864   1812252   1% /dev\n"
"tmpfs                  1815116       560   1814556   1% /dev/shm\n"
"lrm                    1815116      2204   1812912   1%
/lib/modules/2.6.27-14-generic/volatile\n"

So, now, for each line, you want to split as you did and take the 4th element:
irb(main):003:0> s.map {|line| line.split[3]}
=> ["Available", "122649048", "1815116", "1814984", "1815116",
"1812252", "1814556", "1812912"]

If you want to output this array, one element in each line, you can
use puts on the full array:

irb(main):004:0> puts s.map {|line| line.split[3]}
Available
122649048
1815116
1814984
1815116
1812252
1814556
1812912

Hope this helps,

Jesus.