Hi
I am trying to create a script extracting the IP provided by ifconfig.
I tried with grep + awk but I am returned more than I need.

  
/sbin/ifconfig eth0 | grep "inet addr:" | awk '/inet addr:/ { print $2 }'

 
addr:10.15.1.64

awk can grep, no UUOC required.
Please post the output of

/sbin/ifconfig eth0

A bit modification : 

/sbin/ifconfig eth0 | awk -F":" '/inet addr:/ { print $2 }'

/sbin/ifconfig eth0 | grep "inet addr:" | awk '/inet addr:/ { print $2 }' | cut -d":" -f2

/sbin/ifconfig eth0 | grep "inet addr:" | awk '/inet addr:/ { print $2 }' | awf -F":" '{print $2}'

Depending ifconfig's o/p this should also work:

ifconfig eth0 | awk -F":| +" '/inet adr/{print $4}'

Using grep and cut with awk is redundant but piping the result of an awk output to awk is ...

$ ifconfig eth0 | perl -ne 'if ( /inet addr:(^\s]+)/) { print $1; }'