Use a shell variable in awk

You seem to be confusing awk variables and shell variables. awk -v vawk="$1" creates an awk variable called vawk, yet you are trying to use shell syntax ($vawk). This doesn't work because the shell doesn't have a variable called vawk. I think what you want is

awk -v vawk="$1" '$0 ~ vawk { c++ } # ...'
#                      ^ awk variable syntax

^{Reproduced from this now closed as duplicate question as it includes warnings on the limitations of awk variable passing which one might find useful.}

A shell variable is just that: a shell variable. If you want to turn it into a awk variable, you need a syntax such as:

awk -v x="$x" '$2 == x {print $1}' infile

or

awk '$2 == x {print $1}' x="$x" infile

However, those suffer from a problem: escape sequences are expanded in them (and with GNU awk 4.2 or above, if $x starts with @/ and ends in /, it's treated as a regexp type of variable).

So, for instance if the shell variable contains the two characters backslash and n, the awk variable will end up containing the newline character (and with gawk 4.2+, if it contains @/foo/, the awk variable will contain foo and be of type regexp).

Another approach (but which like for -v requires a POSIX awk or nawk (as opposed to the 1970's awk still found as /bin/awk in Solaris)) is to use environment variables:

x="$x" awk '$2 == ENVIRON["x"] {print $1}' infile

Another approach (still with newer awks) is to use the ARGV array in awk:

awk 'BEGIN {x = ARGV[1]; delete ARGV[1]}
  $2 == x {print $1}' "$x" infile