Simple HTTP Server (shell script)

httpserver.sh

#!/bin/sh
#
# Copyright (C) 2017 Upper Stream.
#
# See the bottom of this file for licensing conditions.
#

#set -x
set -e

# program name
program=${0##*/}

usage() {
	cat <<-EOF
	Usage:
	
	$program [-p port] [docroot]
	$program -H
	
	-p port : specify listening port number; defaults to 10080
	-H      : print this help and quit
	docroot : specify document root directory; defaults to the current directory
EOF
}

# default listening port
port=10080

# Configure in accordance with your environment
nc=$(command -v nc) || true

pid_file=/tmp/$program.pid

makefifo() {
	name="$1"
	mkfifo -m 0600 $name.fifo && echo $name.fifo
}

get_content_type() {
	file="$1"
	case $file in
	*.html|*.htm) printf "text/html";;
	*.txt|*.sh)   printf "text/plain";;
	*)            printf "application/octet-stream";;
	esac
}

respond() {
	file="$1"
	length=$(wc -c < $file)
	length=${length##*[!0123456789]}
	content_type=$(get_content_type $file)

	{ cat $fifo2 > /dev/null; printf ""; } > $fifo1 &

	printf "HTTP 200 OK\r\n\Content-Length: $length\r\nContent-Type: $content_type\r\n\r\n" >> $fifo1
	case $content_type in
	text/html|text/plain)
		cat $file >> $fifo1
		;;	
	*)
		dd if=$file of=$fifo1 2> /dev/null
		;;
	esac
	sleep 1; echo "end" > $fifo2
	printf "200 $length"
}

execute_get() {
	if [ "$1" = "/" ]; then
		path="/index.html"
	else
		path=$1
	fi
	file=$docroot$path
	dir=$(cd $(dirname $file); pwd)/
	if echo $dir | grep ^$docroot/ > /dev/null && test -f $file; then
		respond $file
	else
		message="$path not found\r\n"
		printf "HTTP 404 Not Found\r\n\Content-Length: ${#message}\r\n\r\n$message" > $fifo1
		printf "404 -"
	fi
}

execute() {
	method="$1"
	path="$2"
	case $method in
	GET)
		execute_get $path
		;;
	*)
		message="$1 unsupported\r\n_"
		message=${message%_}
		printf "HTTP 501 Not Implemented\r\n\Content-Length: ${#message}\r\n\r\n$message" > $fifo
		printf "501 -"
		;;
	esac
}

cleanup() {
	rm $fifo1 $fifo2 $pid_file
}

interrupt() {
	cleanup
	exit 0
}

get_source_ip() {
	source_ip="xxx.xxx.xxx.xxx"
	if ! ifconfig=$(command -v ifconfig); then
		printf $source_ip
		return
	fi
	if ! sockstat=$(command -v sockstat) && ! netstat=$(command -v netstat); then
		printf $source_ip
		return
	fi
	if [ "$(uname)" = "Linux" ]; then
		myips=$(
			$ifconfig | 
			awk '/^[ \t]*inet / {print substr($2, 6)} /^[ \t]*inet6 / {print substr($3,0,index($3,"/") - 1)}'
		)
	else
		myips=$($ifconfig | grep inet | cut -f2 -d' ')
	fi

	for ip in $myips; do
		if [ "$sockstat"]; then
			source=$($sockstat | grep -F "$ip:$port") || true
			if [ "$source" ]; then
				set -- $source
				source_ip=${7%:*}
				break
			fi
		elif [ "$netstat" ]; then
			source=$($netstat -an | grep -F "$ip:$port") || true
			if [ "$source" ]; then
				set -- $source
				source_ip=${5%:*}
				break
			fi
		fi
	done
	printf "$source_ip"
}

parse() {
	cr=$(printf "\r")
	while read line; do
		line=${line%$cr}
		case "$line" in
		GET*)
			set -- $line
			method=$1
			path=$2
			;;
		Host:*)
			host=${line#Host: }
			;;
		*:*)
			;;
		"")
			source=$(get_source_ip)
			date=$(date +'%d/%m/%Y:%H:%M:%S %z')
			status_length=$(execute $method $path)
			printf "$source - - [$date] $method \"http://$host$path\" $status_length\n"
			trap - INT
			exit
			;;
		*)
			;;
		esac
	done
}

# dependency verification
for cmd in nc; do
	test -z "$(eval echo $"$cmd")" && { echo "$0: \`$cmd\` not found"; exit 2; }
done

while getopts p:H opt; do
	case $opt in
	p) port=$OPTARG;;
	H) usage; exit 255;;
	*) usage; exit 255;;
	esac
done
shift $((OPTIND-1))

if [ $# -eq 0 ]; then
	docroot=.
else
	docroot="$1"
fi
docroot=$(cd $docroot; pwd)

# FIFO to write HTTP response
if ! fifo1=$(makefifo /tmp/${0##*/}.$$.1); then
	echo "$0: creating a named pipe failed.  Already running?" 1>&2
	exit 1
fi

# FIFO for internal event notification
if ! fifo2=$(makefifo /tmp/${0##*/}.$$.2); then
	echo "$0: creating a named pipe failed.  Already running?" 1>&2
	exit 1
fi

trap interrupt INT

echo $$ > $pid_file

cat 1>&2 <<EOF
Simple HTTP Server

Listening at the port number $port.
Type ^C to quit.
EOF

while cat $fifo1 | $nc -l $port | parse; do
	:
done
cleanup
exit

Copyright 2017 Upper Stream.

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in the
Software without restriction, including without limitation the rights to use,
copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
Software, and to permit persons to whom the Software is furnished to do so, subject
to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

For development purpose only; never use in production environment.

• Supports GET method only
• No security consideration
• Somewhat unstable
• POSIX-compliant but requires nc command (or equivalent)

Added support for netstat where sockstat is unavailable.

The following tools are not mandatory but used for logging purpose (foreign ip address retrieval) only:

• awk
• ifconfig
• netstat
• sockstat