Linux/KSH Httpd Server

#! /bin/ksh
#
# httpd.ksh - minimal HTTP-Server (heiner.steven@odn.de)
#
# sanity checking added 2011-05-11 - pokute@caltech.edu
#

PORT=8080  # TCP port to listen to (standard is 80)
ROOT=$HOME # Document root. All paths are relative to this

echo >&2 "listening to port $PORT, documentroot is $ROOT"
while :
do
    # Start 'netcat' in listen mode as server.
    nc -l -p $PORT |&
    exec 3<&p 4>&p # redirect co-process input to fd 3 and 4

    # Read HTTP request header
    requestline=
    while read -u3 line
    do
        # An empty line marks end of request header
        [[ $line = ?(\r) ]] && break
        [[ -z $requestline ]] && requestline=$line
    done
    # Example request line:
    # GET /document.txt HTTP/1.0
    echo >&2 "< REQUEST: $requestline"
    set -- $requestline
    reqtype=$1

    # Create HTTP response header
    file=$ROOT/$2
    [[ -d "$file" ]] && file="$file/index.html"
    # sanity checks using regex - no leading '.', no spaces, no '*', no ';'
    if [[ $reqtype =~ ^GET$ && ! $2 =~ ^\/?\. && ! $file =~ [\*\;\ ]+ && -r $file && -f $file ]]
    then
        print -u4 "HTTP/1.0 200 OK\r"
        print -u4 Content-Length: `wc -c < $file`"\r"
        print -u4 "\r"
        cat "$file" >&4
    else
        print -u4 "HTTP/1.0 404 Not Found\r"
        print -u4 "\r"
    fi
    # Close file descriptors of co-process.
    # This should terminate it:
    exec 3>&- 4>&-
    # "netcat" waits for the other party to close the
    # connection, but the browser will not do this:
    kill -1 $! >/dev/null 2>&1
done