[membash] BASH script which may be used to interact with memcache. All main memcache functions are supported. #memcache

membash.sh

#!/bin/bash

# Gist: 11375877
# Url: https://gist.github.com/goodevilgenius/11375877
#
# All memcache functions are supported.
# 
# Can also be sourced from other scripts, e.g.
#    source membash.sh
#    MCSERVER="localhost"
#    MCPORT=11211
#    foobar=$(mc_get foobar)
#    [ -z "$foobar" ] && foobar="default value"
#    mc_set foobar 0 "$foobar"

# original author: wumin, https://gist.github.com/ri0day/1538831
# updated by goodevilgenius to support debian-based systems, support more
# functions, and be more user-friendly 

mc_usage() {
	format_usage="membash: a memcache library for BASH \n\
https://gist.github.com/goodevilgenius/11375877\n\n\
Usage:\n
	\t $(basename "$0") [-hp] command [arguments] \n \
	\t [-h]\t memcached hostname or ip. \n \
	\t [-p]\t memcached port. \n\n\
Commands: \n \
	\t usage (print this help) \n \
	\t set/add/replace/append/prepend key exptime value \n \
	\t touch key exptime \n \
	\t incr/decr key value \n \
	\t get key \n \
	\t delete key [time] \n \
	\t stats \n \
	\t list_all_keys"
	echo -e $format_usage
}
mc_help() { mc_usage;}

mc_sendmsg() { echo -e "$*\r" | nc $MCSERVER $MCPORT;}

mc_stats() { mc_sendmsg "stats";}

mc_get_last_items_id() {
	LastID=$(mc_sendmsg "stats items"|tail -n 2|head -n 1|awk -F':' '{print $2}')
	echo $LastID
}

mc_list_all_keys() {
	:>/dev/shm/mc_all_keys_${MCSERVER}_${MCPORT}.txt
	max_item_num=$(mc_get_last_items_id)
	for i in `seq 1 $max_item_num`
	  do
		mc_sendmsg "stats cachedump $i 0" | awk '{print $2}'
	done >>/dev/shm/mc_all_keys_${MCSERVER}_${MCPORT}.txt 
	sed -i '/^$/d' /dev/shm/mc_all_keys_${MCSERVER}_${MCPORT}.txt
	cat /dev/shm/mc_all_keys_${MCSERVER}_${MCPORT}.txt
}

mc_get() { mc_sendmsg "get $1" | awk "/^VALUE $1/{a=1;next}/^END/{a=0}a" ;}

mc_touch() {
	key="$1"
	shift
	let exptime="$1"
	shift
	mc_sendmsg "touch $key $exptime"
}

mc_doset() {
	command="$1"
	shift
	key="$1"
	shift
	let exptime="$1"
	shift
	val="$*"
	let bytes=$(echo -n "$val"|wc -c)
	mc_sendmsg "$command $key 0 $exptime $bytes\r\n$val"
}

mc_set() { mc_doset set "$@";}
mc_add() { mc_doset add "$@";}
mc_replace() { mc_doset replace "$@";}
mc_append() { mc_doset append "$@";}
mc_prepend() { mc_doset prepend "$@";}

mc_delete() { mc_sendmsg delete "$*";}
mc_incr() { mc_sendmsg incr "$*";}
mc_decr() { mc_sendmsg decr "$*";}

mc_superpurge() {
	mc_list_all_keys > /dev/null
	if [ ! -z "/dev/shm/mc_all_keys_${MCSERVER}_${MCPORT}.txt" ];then
		grep "$1" /dev/shm/mc_all_keys_${MCSERVER}_${MCPORT}.txt >/dev/shm/temp.swap.${MCSERVER}_${MCPORT}.txt
	fi
	while read keys 
	do
		mc_sendmsg "delete ${keys}"
	done </dev/shm/temp.swap.${MCSERVER}_${MCPORT}.txt

	rm -rf /dev/shm/temp.swap.${MCSERVER}_${MCPORT}.txt
}

if [ "$(basename "$0" .sh)" = "membash" ]
then

	MCSERVER="localhost"
	MCPORT=11211

	while getopts "h:p:" flag
	do
		case $flag in
			h)
				MCSERVER=${OPTARG:="localhost"}
				;;
			p)
				MCPORT=${OPTARG:="11211"}
				;;
			\?)
				echo "Invalid option: $OPTARG" >&2
				;;
		esac
	done
	command="${@:$OPTIND:1}"
	[ -z "$command" ] && command="usage"
	let OPTIND++

	mc_$command "${@:$OPTIND}"

	exit $?

fi

Chking this script with shellcheck shows this comment

script if [ ! -z /dev/shm/mc_all_keys_${MCSERVER}_${MCPORT}.txt ];then
^-- SC2157: Argument to -z is always false due to literal strings.

and indeed the man page for test says

   -z STRING
          the length of STRING is zero

So the question is .. is -z the correct operator?

When I invoke this script interactively with a single argument like "stats" it produces the result but does not close the connection.
I have to use control-C to exit. Everything else is ignored (including the nc command quit)

Perhaps you want to use a HERE statement where the passed argument is expanded and quit appended.
That way the connection closes after doing the required command.
Example
#!/usr/bin/env bash

set -u

command="stats"
nc "myhostname" 11211 << END_OF_INPUT
$command
quit
END_OF_INPUT

mc_sendmsg() { nc "$MCSERVER" "$MCPORT" << END_OF_MSG
$*
quit

END_OF_MSG

perhaps..
}

Or even allow multiple commands enclosing each one in quotes if they have spaces like "stat" "second cmd" ... "stat"
#!/usr/bin/env bash
#
set -u
#
arr_command=( $@ )
( IFS=$'\n'; echo "${arr_command[]}" )
nc "myservername" 11211 << END_OF_INPUT
$( IFS=$'\n'; echo "${arr_command[]}" )
quit
END_OF_INPUT

Please remove the last ^M / CR / carriage-return character:

echo -e "add __TEMPDATA__ 0 600 8\r\ntempdata\r\nquit" | nc localhost 11211

# "tempdata^M"
GET_TEMPDATA1=$(echo -e "get __TEMPDATA__\r\nquit" | nc localhost 11211| awk "/^VALUE $1/{a=1;next}/^END/{a=0}a")
echo -e "${GET_TEMPDATA1} - length(GET_TEMPDATA1)==${#GET_TEMPDATA1}"

# "tempdata"
GET_TEMPDATA2=$(echo -e "get __TEMPDATA__\r\nquit" | nc localhost 11211| awk "/^VALUE $1/{a=1;next}/^END/{a=0}a" | sed 's/\r$//')
echo -e "${GET_TEMPDATA2} - length(GET_TEMPDATA2)==${#GET_TEMPDATA2}"

Rather than the END_OF_INPUT stuffs, I just added -q 0 for immediate disconnect after payload delivery. Change:
nc $MCSERVER $MCPORT
to
nc -q 0 $MCSERVER $MCPORT
at line 40.

Any reason this would not work?