I'd normally write:
export LC_ALL=C
head -n1 "$@" |
tr "\t" "\n" |
awk '{print $1 " " NR-1}'
This works with any number of arguments, or none if there are none. Using "$@"
is important in this and many other contexts. See the Bash manual on special parameters and shell parameter expansion for more information on the many and varied notations available for controlling how shell parameters are handled. Generally, double quotes are a good idea, especially if the file names may contain spaces.