How to insert shell variable inside awk command

If you want to /grep/ with your variable, you have 2 choices :

interface=eth0awk "/$interface/{print}"

or

awk -v interface=eth0 '$0 ~ interface{print}'

See http://www.gnu.org/software/gawk/manual/gawk.html#Using-Shell-Variables

it's like I thought, awk substitutes variables properly, but between //, inside regex ( or awk regex, depending on some awk parameter AFAIR), awk variable cannot be used for substitution

I had no issue grepping with variable inside an awk program (for simple regexp cases):

sawk1='repo\s+module2' sawk2='@project2\s+=\s+module2$'awk "/${sawk1}/,/${sawk2}/"'{print}' aFile

(Here the /xxx/,/yyy/ displays everything between xxx and yyy)
(Note the double-quoted "/${sawk1}/,/${sawk2}/", followed by the single-quoted '{print}')

This works just fine, and comes from "awk: Using Shell Variables in Programs":

A common method is to use shell quoting to substitute the variable’s value into the program inside the script.
For example, consider the following program:

printf "Enter search pattern: "read patternawk "/$pattern/ "'{ nmatches++ }     END { print nmatches, "found" }' /path/to/data

The awk program consists of two pieces of quoted text that are concatenated together to form the program.

• The first part is double-quoted, which allows substitution of the pattern shell variable inside the quotes.
• The second part is single-quoted.

It does add the caveat though:

Variable substitution via quoting works, but can potentially be messy.
It requires a good understanding of the shell’s quoting rules (see Quoting), and it’s often difficult to correctly match up the quotes when reading the program.