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| author | Julio Capote <jcapote@gmail.com> | 2018-11-06 03:03:41 +0000 |
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| committer | Julio Capote <jcapote@gmail.com> | 2018-11-06 03:03:41 +0000 |
| commit | 4b489a049a0063bbb1fd9f0c0f74ce1ee9f87a86 (patch) | |
| tree | 98af5707e30150af482e297bed9cd4e9b5477e6a /content/post/2012-10-07-an-embedded-key-value-store-for-shell-scripts.markdown | |
| parent | a62a3e7755579d93ce3a87243dd277575930fffe (diff) | |
| download | capotej.com-4b489a049a0063bbb1fd9f0c0f74ce1ee9f87a86.tar.gz | |
import old posts
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diff --git a/content/post/2012-10-07-an-embedded-key-value-store-for-shell-scripts.markdown b/content/post/2012-10-07-an-embedded-key-value-store-for-shell-scripts.markdown new file mode 100644 index 0000000..a014a41 --- /dev/null +++ b/content/post/2012-10-07-an-embedded-key-value-store-for-shell-scripts.markdown @@ -0,0 +1,75 @@ +--- +layout: post +title: "an embedded key / value store for shell scripts" +date: 2012-10-07T10:06:00Z +comments: true +categories: ['shell scripting', 'databases'] +--- + +UPDATE: this is now available as a [sub](http://github.com/37signals/sub) command, here: [kiev](http://github.com/capotej/kiev) + +Cooked this up last night when I needed a simple key/value store for use in a shell script: + +```sh db.sh +#!/bin/sh + +DBFILE=example.db + +put(){ + echo "export kv_$1=$2" >> $DBFILE +} + +del(){ + echo "unset kv_$1" >> $DBFILE +} + +get(){ + source $DBFILE + eval r=\$$(echo "kv_$1") + echo $r +} + +list(){ + source $DBFILE + for i in $(env | grep "kv_" | cut -d= -f1 ); do + eval r=\$$i; echo $(echo $i | sed -e 's/kv_//') $r; + done +} + +## cmd dispatch + +if [ ${1:-0} == "set" ]; then + put $2 $3 +elif [ ${1:-0} == "get" ] ; then + get $2 +elif [ ${1:-0} == "list" ] ; then + list +elif [ ${1:-0} == "del" ] ; then + del $2 +else + echo "unknown cmd" +fi +``` + +Use it like so: + + +`$ ./db.sh set foo bar` + +`$ ./db.sh get foo` + +`$ ./db.sh set foo baz` + +`$ ./db.sh get foo` + +`$ ./db.sh del foo` + +`$ ./db.sh list` + + +## How it works + +Every time you update/set/delete a value, it writes a shell expression to an append-only log, +exporting a shell variable (key) with that value. By sourcing the file every time we read a value, we +replay the log, bringing our environment to a consistent state. Then, reading the value is just looking +up that dynamic variable (key) in our shell environment. |