bash script issue

[Bill Thanis]

echo $((078+1)) -> bash: 078: value too great for base (error token is
"078")

Octal has digits 0-7 8 is not a number in octal.

Bill



On Wed, Sep 3, 2014 at 6:55 PM, Walter Dnes <waltdnes-SLHPyeZ9y/tg9hUCZPvPmw at public.gmane.org> wrote:

> On Wed, Sep 03, 2014 at 03:19:49PM +0000, Peter wrote
> > D. Hugh Redelmeier <hugh at ...> writes:
> >
> > > I don't remember an ordinary shell context where a pathname can be
> > > confused with number.  Can you give an example?
> >
> > Ordinary not, but:
> >
> > echo $((07+1)) -> 8 (yes... why?)
> > echo $((007+1)) -> 8 (hmm, must be Mr. Bond)
> > echo $((077+1)) -> 64 (no kidding, 077oct is 64dec)
> > echo $((078+1)) -> bash: 078: value too great for base (error token is
> "078")
> >
> > So if you do any math on any numbers for example numbered files like
> > DCIM/IMG0077.jpg you WILL likely be bitten. I think the 1st application
> > where I was bitten was many years ago trying to figure out missing and
> > duplicate IMGnnnnn.jpg files in a large recovered image directory. I also
> > tried to be clever and rename files such that there would be no gaps upon
> > finding missing files, in one pass. That did not go well, I had a 10% or
> so
> > file loss when done. There are many other 'opportunities' to get bitten.
>
>   I use bash in many cases where other people would use "R" or whatever.
> Leading zeros in numbers come up so often, I've written my own function
> to handle the situation.  You can include it at the top of a program
> like so...
>
> #!/bin/bash
> #
> # bash treats leading zeros as indicating octal, freaks out on 08 or 09,
> # and numbers 010 and above are just plain wrong.  So strip leading zeros.
> strip_leading_0() {
>    stripped="${1}"
> #
> # Leave plain "0" alone.  Only strip zeros if string is longer
> # than one character.
>    while [ ${#stripped} -gt 1 ] && [ "${stripped:0:1}" == "0" ]
>    do
>       stripped=${stripped:1}
>    done
>    export stripped
> }
> ...
> #
> # "Sanitize" numeric variable foobar
> strip_leading_0 ${foobar}
> foobar=${stripped}
>
> ...or you can set up and load a common function library as shown at
> http://bash.cyberciti.biz/guide/Shell_functions_library
>
> --
> Walter Dnes <waltdnes-SLHPyeZ9y/tg9hUCZPvPmw at public.gmane.org>
> I don't run "desktop environments"; I run useful applications
> --
> The Toronto Linux Users Group.      Meetings: http://gtalug.org/
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