A templating script written in bash

templater.bash

#!/bin/bash
if [[ $# -eq 0 ]]; then
    echo "Usage:"
    echo "  templater key=value ... inputfile"
    echo
    echo "Sample input file:"
    echo "  Hello \${name}, enjoy templater!"
    echo
    echo "Sample output:"
    echo "  $ ./templater name=Affo input"
    echo "  Hello Affo, enjoy templater!"
    echo
    exit
fi

args=( "$@" )
fname=${args[${#args[@]}-1]}
unset "args[${#args[@]}-1]"

cmd="sed"
for arg in "${args[@]}"; do
    if [[ "$arg" != *"="* ]]; then
        continue
    fi

    key="${arg%=*}"
    value="${arg#*=}"
    cmd="$cmd -e 's/\${$key}/$value/g'"
done

cmd="$cmd $fname"

eval $cmd