#!/bin/sh

if [ "$1" == "parameter" ]
then
    while read line
    do
        #echo "$line"
    done <$1
else
    echo "Not working"
fi

#!/bin/sh

if [ "$1" = "-parameter" ]
then
    while read line
    do
        #echo "$line"
    done <$2   # Use $2 instead of $1 here.  Or use shift
else
    echo "Not working" >&2
fi