Wget on pure Bash

wget_on_bash.sh

#!/usr/bin/env bash

#
# Program: Wget on pure bash <wget_on_bash.sh>
#
# Author: Mikhail Grigorev <sleuthhound at gmail dot com>
#
# Current Version: 1.0.0
#
# License:
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
#

_usage() {
    echo ""
    echo "Usage: $0 \"http://http.programs74.ru/\" \"/tmp/result\""
    echo ""
    exit 1
}

[ $# -ne 2 ] && _usage

# wget on bash
function _wget() {
    local URL=$1
    local LOCALFILE=${2:-"/tmp/test"}
    local TMPFILE=$2.tmp
    read proto server path <<<$(echo ${URL//// })
    local SCHEME=${proto//:*}
    local PATH=/${path// //}
    local HOST=${server//:*}
    local PORT=${server//*:}
    if [[ "${SCHEME}" != "http" ]]; then
        echo "ERROR: Sorry, support only http protocol."
        return 1
    fi
    if [[ "${HOST}" = "${PORT}" ]]; then
        PORT=80
    fi
    # Open tcp connection and check hostname/port
    (exec 3<>/dev/tcp/${HOST}/${PORT}) >/dev/null 2>&1
    if [ $? -ne 0 ]; then
        echo "ERROR: Name or service not known."
        return $?
    fi
    # Close tcp
    exec 3>&-
    # Open tcp connection
    exec 3<>/dev/tcp/${HOST}/${PORT}
    echo -en "GET ${PATH} HTTP/1.1\r\nHost: ${HOST}\r\nConnection: close\r\nContent-Length: 0\r\n\r\n" >&3
    if [ $? -ne 0 ]; then
        return $?
    fi
    /bin/cat <&3 > "${TMPFILE}"
    /bin/tail "${TMPFILE}" -n +$((`/bin/sed "${TMPFILE}" -e '/^\r$/q' | /bin/wc -l`+1)) > "${LOCALFILE}"
    /bin/rm -f "${TMPFILE}" >/dev/null 2>&1
    # Close tcp
    exec 3>&-
}

if [ -f "$2" ]; then
    echo "ERROR: File '$2' already exist."
    exit 1
fi

echo "Downloading '$1' and save to '$2'"
_wget "$1" "$2"
if [ -f "$2" ]; then
    echo "Download done, check file ;)"
else
    echo "ERROR: Something went wrong."
    exit 1
fi