What I am looking to do is suing sed come up with a way that if the value of
a variable is piped to sed and if the variable contains a non-number
character the whole thing becomes the word 'null'

something like:


t=999

echo $t | sed 's/[^0-9]/null/'

it allows the 999 to be printed which is great

but if I do

t=99u99k4

echo $t | sed 's/[^0-9]/null/'

I get   99null99k4

I really am looking for just the word   'null'  to come out.

How can I do this

Thanks

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On 2006-12-22, Oxnard wrote:
> What I am looking to do is suing sed come up with a way that if the value 
of
> a variable is piped to sed and if the variable contains a non-number
> character the whole thing becomes the word 'null'
>
> something like:
>
>
> t=999
>
> echo $t | sed 's/[^0-9]/null/'
>
> it allows the 999 to be printed which is great
>
> but if I do
>
> t=99u99k4
>
> echo $t | sed 's/[^0-9]/null/'
>
> I get   99null99k4
>
> I really am looking for just the word   'null'  to come out.
>
> How can I do this

If you want to check a single variable (or even several), you don't
need sed. Save that for files.

case $t in
*[!0-9]*) echo null ;;
*) echo "$t" ;;
esac

--
Chris F.A. Johnson, author        <http://cfaj.freeshell.org/shell>
Shell Scripting Recipes: A Problem-Solution Approach (2005, Apress)
===== My code in this post, if any, assumes the POSIX locale
===== and is released under the GNU General Public Licence

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Oxnard wrote:
> What I am looking to do is suing sed come up with a way that if the value 
of
> a variable is piped to sed and if the variable contains a non-number
> character the whole thing becomes the word 'null'
>
> something like:
>
>
> t=999
>
> echo $t | sed 's/[^0-9]/null/'
>
> it allows the 999 to be printed which is great
>
> but if I do
>
> t=99u99k4
>
> echo $t | sed 's/[^0-9]/null/'
>
> I get   99null99k4
>
> I really am looking for just the word   'null'  to come out.
>

As Chris pointed out, use shell expression.
With sed, you must change the regex to match the entire line,
so the entire line is replaced:

sed 's/.*[^0-9].*/null/'


--
Michael Tosch @ hp : com

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