minor perl/awk tip

[Robin Battey]

Thanks, didn't know about the -ne option.  

My first draft used awk instead of perl, too, but I couldn't remember 
offhand the syntax to change the field separator.  But, after getting 
off my duff and looking it up, here 'tis:

  $ /sbin/ip addr show dev eth0 |
    awk 'BEGIN { FS = "[ \t/]+" } /inet/ { print $3; }'

Whee-hah.  And, for completeness' sake, here's an awk script that will 
get all of them in that nicely formatted list:

  $ /sbin/ip addr show | 
    awk 'BEGIN { FS = "[ \t/]+" } 
    /^[0-9]+:/ { printf "%s", $2; } 
    /inet/ { printf "\t%s\n", $3; }'

As usual, mangle the awk to get whatever output you desire.

Cheers!
-robin

P.S. the reason it's now $3 instead of $2 is because the default 
behavior of awk is "special", and it strips leading and trailing 
whitespace.  That only happens when the value of FS is " " (a single 
space).  So, because I changed FS, $1 is *before* fir first space, and
is therefore blank -- making $2 "inet" and $3 the ip address.


On Tue, Jan 21, 2003 at 02:43:19PM -0800, Evan Martin wrote:
> On Tue, Jan 21, 2003 at 01:59:18PM -0800, Robin Battey wrote:
> >   $ /sbin/ip addr show dev eth0 | perl -e 'while (<>) {
> >     m#inet\s+(.+)/# and print "$1\n"; }'
> 
> Equivalent perl (because that loop is such a common construct):
> 
>   perl -e 'while (<>) { foo; }'
>   perl -ne 'foo;'
> 
> Or even simpler, use awk:
>   $ ip addr show dev eth0 | awk '$1 ~ /inet/ { print $2 }'
>   10.0.0.2/24
> 
> or maybe just:
>   $ ip addr show dev eth0 | awk '/inet/ { print $2 }'
> 
> (...though that doesn't strip the mask like yours does.)
> 
>  --evan, who just helped out an awk tutorial and has awk on the brain.
> 
> -- 
>       Evan Martin
> martine at cs.washington.edu
>   http://neugierig.org

-- 
                        Robin Battey

     90CF 2E8F 8A96 D0C0 09A2  9CFE C130 6CD4 6DC3 6DCF
              http://www.zanfur.com/zanfur.pub
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