Using a configmap as a simple queue with kubectl

cm-queue.sh

#!/bin/bash

ns=$1
cm=$2
cmkey=$3
# actions: getfirst, getlast, getall, getyaml, shift, pop, prepend, append, delete
action=$4
cmval=$5
k="kubectl -n $ns"
jp="jsonpath='{.data.$cmkey}'"
er=0
usage="Usage: ./cm-queue.sh [namespace] [configmap-name] [queue-name] [getfirst|getlast|getall|getyaml|shift|pop|prepend|append|delete] [value]"
[ -z "$ns" ] && echo "Must define a namespace" && echo $usage && exit 1
[ -z "$cm" ] && echo "Must define a configmap name" && echo $usage && exit 1
[ -z "$cmkey" ] && echo "Must define a queue name (configmap key)" && echo $usage && exit 1
[ -z "$action" ] && echo "Must define an action" && echo $usage && exit 1

# If the queue doesn't exist... make it ¯\_(ツ)_/¯
if [ -z "$($k get cm $cm --ignore-not-found=true)" ]; then
    create=$($k create cm $cm)
fi
function getall() {
    $k get cm $cm -o $jp | tr ' ' '\n' | sed -e "s/'//g"
}
function trim() {
    echo "$1" | sed 's/^  *//' | sed 's/  *$//g'
}
# getfirst: Get item from beginning of list
if [ $action == "getfirst" ]; then
    getall | head -1 && er=1
fi

# getlast: Get item from end of list
if [ $action == "getlast" ]; then
    getall | tail -1 && er=1
fi

# getall: Get full list
if [ $action == "getall" ]; then
    getall && er=1
fi

# getyaml: get yaml
if [ $action == "getyaml" ]; then
    $k get cm $cm -o yaml && er=1
fi

# shift: Remove item from beginning of list
if [ $action == "shift" ]; then
    first=$(getall | head -1)
    queue="$(getall | tail -n +2 | tr '\n' ' ')"
    patch=$($k patch cm $cm --patch='{"data": {"'"$cmkey"'": "'"$(trim "$queue")"'"}}')
    echo "$first" && er=1
fi

# pop: Remove item from end of list
if [ $action == "pop" ]; then
    last=$(getall | tail -1)
    len=$(getall | wc -l | awk '{print $1}')
    if [ $len -gt 0 ]; then
        queue="$(getall | head -n $((len)) | tr '\n' ' ')"
    else
        queue=""
    fi
    patch=$($k patch cm $cm --patch='{"data": {"'"$cmkey"'": "'"$(trim "$queue")"'"}}')
    echo "$last" && er=1
fi

# prepend: Add item to beginning of list
if [ $action == "prepend" ]; then
    [ -z "$cmval" ] && echo "Must define a configmap queue value to prepend" && echo $usage && exit 1
    queue="$cmval $(getall | tr '\n' ' ')"
    patch=$($k patch cm $cm --patch='{"data": {"'"$cmkey"'": "'"$(trim "$queue")"'"}}')
    getall && er=1
fi

# append: Add item to end of list
if [ $action == "append" ]; then
    [ -z "$cmval" ] && echo "Must define a configmap queue value to append" && echo $usage && exit 1
    queue="$(getall | tr '\n' ' ') $cmval"
    patch=$($k patch cm $cm --patch='{"data": {"'"$cmkey"'": "'"$(trim "$queue")"'"}}')
    getall && er=1
fi

# delete: delete the whole configmap
if [ $action == "delete" ]; then
    $k delete cm $cm && er=1
fi

if [ $er -eq 0 ]; then
    echo "Error: action[\"$action\"] failed."
    [ -n "$patch" ] && echo "$patch"
    echo "$usage"
    exit 1
fi