command_not_found_handler.sh

# tested in zsh

# Don't try this at home.
command_not_found_handler() {

    replaced=false

    set -A args "$@"

    # aliases like gcc-O2='gcc -O2'
    if [ $args[1] =~ "^([^-]+)(-.+)$" ]; then
        shift args
        set -A args $match[1] $match[2] $args
        replaced=true
    fi

    # aliases like find.='find .'
    if [ $args[1] =~ "^(.*[^.])(\.+)$" ]; then
        cmd=$match[1]
        arg=$match[2]

        if [ $arg =~ "^(\.|\.\.)$" ]; then
            dir=$arg
        else
            dir=".."
            for i in {3..${#arg}}; do
                dir="$dir/.."
            done
        fi

        shift args
        set -A args $cmd $dir $args
        replaced=true
    fi

    # aliases like stglog4f='stg log -n 4 -f'
    if [ $args[1] =~ "^(stg|git|hg|svn)log([0-9]+)(.*)$" ]; then

        vcs=$match[1]

        case $vcs in
            stg|git) opt=-n ;;
            *)       opt=-l ;;
        esac

        shift args

        if [ -z $match[3] ]; then
            set -A args $vcs log $opt $match[2] $args
        else
            set -A args $vcs log $opt $match[2] -$match[3] $args
        fi
        replaced=true
    fi

    # aliases like gitst='git st'
    if [ $args[1] =~ "^(hg|git|stg|svn|brew|jar|tar|sudo)(.+)" ]; then
        shift args
        set -A args $match[1] $match[2] $args
        replaced=true
    fi

    # aliases like egreprw='egrep -rw'
    if [ $args[1] =~ "^(ls|z?(e|f)?grep|du|df|wc|make|last|netstat)(.+)$" ]; then
        shift args
        set -A args $match[1] -$match[3] $args
        replaced=true
    fi

    # we are in subprocess here, so `cd` and other builtins do not work
    if [ $args[1] =~ "^(cd|set)$" ]; then
        return 1
    fi

    # do not call exec if nothing is changed to avoid endless recursion
    if $replaced; then
        #echo $args >&2
        exec $args
    fi

    return 1
}