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Re: Recomended tutoial(s) on doing arithmetic in Bash scripts

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On 03/05/2017 02:23 PM, tomas@tuxteam.de wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> On Sun, Mar 05, 2017 at 12:10:43PM -0600, Richard Owlett wrote:
>
> [...]
>
>> How about the whole app <grin>
>> You solved my problem with one line.
>
> Glad it helped :)
>
> [...]
>
>> I needed to report the number of bytes downloaded for each portion
>> of a project [...]
>
> Let me pick a nit...
>
>> mystring=$(echo $(grep "usb0" /proc/net/dev))
>
> This should be equivalent to
>
>   mystring=$(grep "usb0" /proc/net/dev)

I was just copying the tutorial's syntax. I had no explanations, only 
code fragments. One of the sites that prompted me to ask for 
recommendations.

>
> (background:
>
>   - grep "usb0"/proc/net/dev
>     spits out the line(s) containing the pattern "usb0"
>
>   - the $(...) around it expands it in the shell inline
>
>   - the echo spits that again out to stdout
>
>   - the $(...) around it expands it again in-line
>
> So unless the expansion is doing anything funky (which we won't hope,
> but see below), you can unwrap the outer $(echo ...).
>
> Now the second nit: I'm not sure whether there's a case when the
> unquoted $(...) might undergo a further expansion by the shell,
> so it's prudent to quote it, like so:
>
>   mystring="$(grep "usb0" /proc/net/dev)"
>
> (I know, my example wasn't... exemplar in this respect, but I knew
> I was only getting plain numbers and I was kind of lazy: bad tomás)
>
>> Someone on another group wanted me to use LibreOffice Calc ;/
>
> Might work, but don't ask me how :-/

That poster's explanation made little sense. Only one of the reasons I 
didn't try it.

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Thread

Recomended tutoial(s) on doing arithmetic in Bash scripts Richard Owlett <rowlett@cloud85.net> - 2017-03-05 16:50 +0100
  Re: Recomended tutoial(s) on doing arithmetic in Bash scripts Reco <recoverym4n@gmail.com> - 2017-03-05 17:30 +0100
  Re: Recomended tutoial(s) on doing arithmetic in Bash scripts <tomas@tuxteam.de> - 2017-03-05 17:30 +0100
    Re: Recomended tutoial(s) on doing arithmetic in Bash scripts GiaThnYgeia <GiaThnYgeia@openmailbox.org> - 2017-03-05 19:20 +0100
      Re: Recomended tutoial(s) on doing arithmetic in Bash scripts <tomas@tuxteam.de> - 2017-03-05 21:40 +0100
      Re: Recomended tutoial(s) on doing arithmetic in Bash scripts Greg Wooledge <wooledg@eeg.ccf.org> - 2017-03-06 14:40 +0100
        Re: Recomended tutoial(s) on doing arithmetic in Bash scripts <tomas@tuxteam.de> - 2017-03-06 15:00 +0100
        Re: Recomended tutoial(s) on doing arithmetic in Bash scripts Jörg-Volker Peetz <jvpeetz@web.de> - 2017-03-06 16:00 +0100
          Re: Recomended tutoial(s) on doing arithmetic in Bash scripts <tomas@tuxteam.de> - 2017-03-06 16:40 +0100
    Re: Recomended tutoial(s) on doing arithmetic in Bash scripts Richard Owlett <rowlett@cloud85.net> - 2017-03-05 19:20 +0100
      Re: Recomended tutoial(s) on doing arithmetic in Bash scripts Richard Owlett <rowlett@cloud85.net> - 2017-03-05 19:50 +0100
      Re: Recomended tutoial(s) on doing arithmetic in Bash scripts <tomas@tuxteam.de> - 2017-03-05 21:30 +0100
        Re: Recomended tutoial(s) on doing arithmetic in Bash scripts Richard Owlett <rowlett@cloud85.net> - 2017-03-05 22:00 +0100
    Re: Recomended tutoial(s) on doing arithmetic in Bash scripts Jude DaShiell <jdashiel@panix.com> - 2017-03-05 23:20 +0100
      Re: Recomended tutoial(s) on doing arithmetic in Bash scripts Richard Owlett <rowlett@cloud85.net> - 2017-03-06 12:20 +0100
        Re: Recomended tutoial(s) on doing arithmetic in Bash scripts <tomas@tuxteam.de> - 2017-03-06 12:40 +0100
  Re: Recomended tutoial(s) on doing arithmetic in Bash scripts David Christensen <dpchrist@holgerdanske.com> - 2017-03-05 20:50 +0100
    Re: Recomended tutoial(s) on doing arithmetic in Bash scripts Richard Owlett <rowlett@cloud85.net> - 2017-03-05 21:50 +0100
      Re: Recomended tutoial(s) on doing arithmetic in Bash scripts David Christensen <dpchrist@holgerdanske.com> - 2017-03-06 04:40 +0100
    Re: Recomended tutoial(s) on doing arithmetic in Bash scripts <tomas@tuxteam.de> - 2017-03-05 22:30 +0100
  Re: Recomended tutoial(s) on doing arithmetic in Bash scripts Jude DaShiell <jdashiel@panix.com> - 2017-03-05 23:10 +0100

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