Re: Recomended tutoial(s) on doing arithmetic in Bash scripts
- Date: Sun, 5 Mar 2017 21:23:41 +0100
- From: <tomas@xxxxxxxxxx>
- Subject: Re: Recomended tutoial(s) on doing arithmetic in Bash scripts
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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)
- 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 :-/
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