From 1153d654d807bdef5088c90e025f498c82ffaa60 Mon Sep 17 00:00:00 2001
From: "Kay Marquardt (Gnadelwartz)" <kay@rrr.de>
Date: Wed, 23 Sep 2020 10:58:18 +0200
Subject: [PATCH] check for bash features

---
 README.html      | 77 +++++++++++++++++++++++++-----------------------
 README.md        | 10 +++++--
 README.txt       | 12 +++++---
 bashbot.sh       | 15 +++++++++-
 doc/0_install.md | 18 ++++++++++-
 5 files changed, 86 insertions(+), 46 deletions(-)

diff --git a/README.html b/README.html
index 260cc8c..7e58e16 100644
--- a/README.html
+++ b/README.html
@@ -94,6 +94,7 @@ Written by Drew (@topkecleon) and Kay M (@gnadelwartz).
 <p>Uses <a href="http://github.com/dominictarr/JSON.sh">JSON.sh</a> and the magic of sed.</p>
 <p>Even bashbot is written in bash, it depends on commands typically available in a Unix/Linux Environment. More concrete on the common commands provided by recent versions of <a href="https://en.wikipedia.org/wiki/List_of_GNU_Core_Utilities_commands">coreutils</a>, <a href="https://en.wikipedia.org/wiki/BusyBox#Commands">busybox</a> or <a href="https://landley.net/toybox/help.html">toybox</a>, see <a href="doc/7_develop.md#common-commands">Developer Notes</a></p>
 <p><em>Note for MacOS and BSD Users:</em> As bashbot heavily uses modern bash and (gnu) grep/sed features, bashbot will not run without installing additional software, see <a href="doc/0_install.md">Install Bashbot</a></p>
+<p><em>Note for emmbedded systems:</em> busybox or toybox ONLY is not sufficient, you need a to install a "real" bash, see <a href="doc/0_install.md">Install Bashbot</a></p>
 <p>Bashbot <a href="https://github.com/topkecleon/telegram-bot-bash">Documentation</a> and <a href="https://github.com/topkecleon/telegram-bot-bash/releases">Downloads</a> are available on www.github.com</p>
 <h2>Documentation</h2>
 <ul>
@@ -157,9 +158,11 @@ Written by Drew (@topkecleon) and Kay M (@gnadelwartz).
 <p>To install and run bashbot you need access to a linux/unix command line. If you don't know how to get access to a linux/unix command line you should stop reading here :-(</p>
 <p>In addition you need a <a href="https://telegram.org">Telegram client</a> and a mobile phone to <a href="https://telegramguide.com/create-a-telegram-account/">register an account</a>. If you don't want to register for Telegram you should stop reading here ;-)</p>
 <p>After you're registered to Telegram send a message to <a href="https://telegram.me/botfather">@botfather</a>, <a href="doc/1_firstbot.md">create a new Telegram Bot token</a> and write it down. You need the token to install the bot.</p>
-<p>Now open a terminal and check if bash is installed: <code>which bash &amp;&amp; echo "bash installed!"</code>. If you get an error message bash is not installed.</p>
+<p>Now open a terminal and check if bash is installed:</p>
+<pre><code>which bash &amp;&amp; echo &quot;bash seems available...&quot;
+</code></pre>
 <p>Create a new directory, change to it: <code>mkdir tbb; cd tbb</code> and download the latest '*.tar.gz' file from <a href="https://github.com/topkecleon/telegram-bot-bash/releases">https://github.com/topkecleon/telegram-bot-bash/releases</a>. This can be done with the commands:</p>
-<div class="sourceCode" id="cb1"><pre class="sourceCode bash"><code class="sourceCode bash"><a class="sourceLine" id="cb1-1" title="1"><span class="fu">wget</span> -q https://github.com/<span class="va">$(</span><span class="fu">wget</span> -q https://github.com/topkecleon/telegram-bot-bash/releases/latest -O - <span class="kw">|</span> <span class="fu">egrep</span> <span class="st">&#39;/.*/.*/.*tar.gz&#39;</span> -o<span class="va">)</span></a></code></pre></div>
+<div class="sourceCode" id="cb2"><pre class="sourceCode bash"><code class="sourceCode bash"><a class="sourceLine" id="cb2-1" title="1"><span class="fu">wget</span> -q https://github.com/<span class="va">$(</span><span class="fu">wget</span> -q https://github.com/topkecleon/telegram-bot-bash/releases/latest -O - <span class="kw">|</span> <span class="fu">egrep</span> <span class="st">&#39;/.*/.*/.*tar.gz&#39;</span> -o<span class="va">)</span></a></code></pre></div>
 <p>Extract the '*.tar.gz' file and change to bashbot directory: <code>tar -xzf *.tar.gz; cd telegram-bot-bash</code>, install bashbot: <code>./bashbot.sh init</code> and enter your bot token when asked. All other questions can be answered by hitting the &lt;Return&gt; key.</p>
 <p>That's all, now you can start your bot with <code>./bashbot.sh start</code> and send him messages:</p>
 <pre><code>/start
@@ -196,18 +199,18 @@ It features background tasks and interactive chats, and can serve as an interfac
 <p>A powerful tool to improve your scripts is <code>shellcheck</code>. You can <a href="https://www.shellcheck.net/">use it online</a> or <a href="https://github.com/koalaman/shellcheck#installing">install shellcheck locally</a>. Shellcheck is used extensively in bashbot development to ensure a high code quality, e.g. it's not allowed to push changes without passing all shellcheck tests. In addition bashbot has a <a href="doc/7_develop.md">test suite</a> to check if important functionality is working as expected.</p>
 <h3>Use printf whenever possible</h3>
 <p>If you're writing a script and it is taking external input (from the user as arguments or file system...), you shouldn't use echo to display it. <a href="https://unix.stackexchange.com/a/6581">Use printf whenever possible</a></p>
-<div class="sourceCode" id="cb4"><pre class="sourceCode bash"><code class="sourceCode bash"><a class="sourceLine" id="cb4-1" title="1">  <span class="co"># very simple</span></a>
-<a class="sourceLine" id="cb4-2" title="2">  <span class="bu">echo</span> <span class="st">&quot;text with variables. PWD=</span><span class="va">$PWD</span><span class="st">&quot;</span></a>
-<a class="sourceLine" id="cb4-3" title="3">  <span class="bu">printf</span> <span class="st">&#39;%s\n&#39;</span> <span class="st">&quot;text with variables. PWD=</span><span class="va">$PWD</span><span class="st">&quot;</span></a>
-<a class="sourceLine" id="cb4-4" title="4">  <span class="ex">-</span><span class="op">&gt;</span> text with variables. PWD=/home/xxx</a>
-<a class="sourceLine" id="cb4-5" title="5"></a>
-<a class="sourceLine" id="cb4-6" title="6">  <span class="co"># more advanced</span></a>
-<a class="sourceLine" id="cb4-7" title="7">  <span class="va">FLOAT=</span><span class="st">&quot;1.2346777892864&quot;</span> <span class="va">INTEGER=</span><span class="st">&quot;12345.123&quot;</span></a>
-<a class="sourceLine" id="cb4-8" title="8">  <span class="bu">echo</span> <span class="st">&quot;text with variabeles. float=</span><span class="va">$FLOAT</span><span class="st">, integer=</span><span class="va">$INTEGER</span><span class="st">, PWD=</span><span class="va">$PWD</span><span class="st">&quot;</span></a>
-<a class="sourceLine" id="cb4-9" title="9">  <span class="ex">-</span><span class="op">&gt;</span>text with variables. float=1.2346777892864, integer=12345.123, PWD=/home/xxx</a>
-<a class="sourceLine" id="cb4-10" title="10"></a>
-<a class="sourceLine" id="cb4-11" title="11">  <span class="bu">printf</span> <span class="st">&quot;text with variables. float=%.2f, integer=%d, PWD=%s\n&quot;</span> <span class="st">&quot;&quot;</span> <span class="st">&quot;</span><span class="va">$INTEGER</span><span class="st">&quot;</span> <span class="st">&quot;</span><span class="va">$PWD</span><span class="st">&quot;</span></a>
-<a class="sourceLine" id="cb4-12" title="12">  <span class="ex">-</span><span class="op">&gt;</span>text with variables. float=1.23, integer=12345, PWD=/home/xxx</a></code></pre></div>
+<div class="sourceCode" id="cb5"><pre class="sourceCode bash"><code class="sourceCode bash"><a class="sourceLine" id="cb5-1" title="1">  <span class="co"># very simple</span></a>
+<a class="sourceLine" id="cb5-2" title="2">  <span class="bu">echo</span> <span class="st">&quot;text with variables. PWD=</span><span class="va">$PWD</span><span class="st">&quot;</span></a>
+<a class="sourceLine" id="cb5-3" title="3">  <span class="bu">printf</span> <span class="st">&#39;%s\n&#39;</span> <span class="st">&quot;text with variables. PWD=</span><span class="va">$PWD</span><span class="st">&quot;</span></a>
+<a class="sourceLine" id="cb5-4" title="4">  <span class="ex">-</span><span class="op">&gt;</span> text with variables. PWD=/home/xxx</a>
+<a class="sourceLine" id="cb5-5" title="5"></a>
+<a class="sourceLine" id="cb5-6" title="6">  <span class="co"># more advanced</span></a>
+<a class="sourceLine" id="cb5-7" title="7">  <span class="va">FLOAT=</span><span class="st">&quot;1.2346777892864&quot;</span> <span class="va">INTEGER=</span><span class="st">&quot;12345.123&quot;</span></a>
+<a class="sourceLine" id="cb5-8" title="8">  <span class="bu">echo</span> <span class="st">&quot;text with variabeles. float=</span><span class="va">$FLOAT</span><span class="st">, integer=</span><span class="va">$INTEGER</span><span class="st">, PWD=</span><span class="va">$PWD</span><span class="st">&quot;</span></a>
+<a class="sourceLine" id="cb5-9" title="9">  <span class="ex">-</span><span class="op">&gt;</span>text with variables. float=1.2346777892864, integer=12345.123, PWD=/home/xxx</a>
+<a class="sourceLine" id="cb5-10" title="10"></a>
+<a class="sourceLine" id="cb5-11" title="11">  <span class="bu">printf</span> <span class="st">&quot;text with variables. float=%.2f, integer=%d, PWD=%s\n&quot;</span> <span class="st">&quot;&quot;</span> <span class="st">&quot;</span><span class="va">$INTEGER</span><span class="st">&quot;</span> <span class="st">&quot;</span><span class="va">$PWD</span><span class="st">&quot;</span></a>
+<a class="sourceLine" id="cb5-12" title="12">  <span class="ex">-</span><span class="op">&gt;</span>text with variables. float=1.23, integer=12345, PWD=/home/xxx</a></code></pre></div>
 <h3>Do not use #!/usr/bin/env bash</h3>
 <p><strong>We stay with /bin/bash shebang, because it's more save from security perspective.</strong></p>
 <p>Use of a fixed path to the system provided bash makes it harder for attackers or users to place alternative versions of bash and avoids using a possibly broken, mangled or compromised bash executable.</p>
@@ -237,38 +240,38 @@ It features background tasks and interactive chats, and can serve as an interfac
 <h3>Can I send messages from CLI and scripts?</h3>
 <p>Of course, you can send messages from CLI and scripts, simply install bashbot as <a href="#Your-really-first-bashbot-in-a-nutshell">described here</a>, send the message '/start' to set yourself as botadmin and stop the bot with <code>./bashbot.sh stop</code>.</p>
 <p>Run the following commands in your bash shell or script while you are in the installation directory:</p>
-<div class="sourceCode" id="cb5"><pre class="sourceCode bash"><code class="sourceCode bash"><a class="sourceLine" id="cb5-1" title="1"><span class="co"># prepare bash / script to send commands</span></a>
-<a class="sourceLine" id="cb5-2" title="2"><span class="bu">export</span> <span class="va">BASHBOT_HOME=</span><span class="st">&quot;</span><span class="va">$(</span><span class="bu">pwd</span><span class="va">)</span><span class="st">&quot;</span></a>
-<a class="sourceLine" id="cb5-3" title="3"><span class="bu">source</span> ./bashbot.sh source</a>
-<a class="sourceLine" id="cb5-4" title="4"></a>
-<a class="sourceLine" id="cb5-5" title="5"><span class="co"># send me a test message</span></a>
-<a class="sourceLine" id="cb5-6" title="6"><span class="ex">send_message</span> <span class="st">&quot;</span><span class="va">$(</span><span class="ex">getConfigKey</span> <span class="st">&quot;botadmin&quot;</span><span class="va">)</span><span class="st">&quot;</span> <span class="st">&quot;test&quot;</span></a>
-<a class="sourceLine" id="cb5-7" title="7"></a>
-<a class="sourceLine" id="cb5-8" title="8"><span class="co"># send me output of a system command</span></a>
-<a class="sourceLine" id="cb5-9" title="9"><span class="ex">send_message</span> <span class="st">&quot;</span><span class="va">$(</span><span class="ex">getConfigKey</span> <span class="st">&quot;botadmin&quot;</span><span class="va">)</span><span class="st">&quot;</span> <span class="st">&quot;</span><span class="va">$(</span><span class="fu">df</span> -h<span class="va">)</span><span class="st">&quot;</span></a></code></pre></div>
+<div class="sourceCode" id="cb6"><pre class="sourceCode bash"><code class="sourceCode bash"><a class="sourceLine" id="cb6-1" title="1"><span class="co"># prepare bash / script to send commands</span></a>
+<a class="sourceLine" id="cb6-2" title="2"><span class="bu">export</span> <span class="va">BASHBOT_HOME=</span><span class="st">&quot;</span><span class="va">$(</span><span class="bu">pwd</span><span class="va">)</span><span class="st">&quot;</span></a>
+<a class="sourceLine" id="cb6-3" title="3"><span class="bu">source</span> ./bashbot.sh source</a>
+<a class="sourceLine" id="cb6-4" title="4"></a>
+<a class="sourceLine" id="cb6-5" title="5"><span class="co"># send me a test message</span></a>
+<a class="sourceLine" id="cb6-6" title="6"><span class="ex">send_message</span> <span class="st">&quot;</span><span class="va">$(</span><span class="ex">getConfigKey</span> <span class="st">&quot;botadmin&quot;</span><span class="va">)</span><span class="st">&quot;</span> <span class="st">&quot;test&quot;</span></a>
+<a class="sourceLine" id="cb6-7" title="7"></a>
+<a class="sourceLine" id="cb6-8" title="8"><span class="co"># send me output of a system command</span></a>
+<a class="sourceLine" id="cb6-9" title="9"><span class="ex">send_message</span> <span class="st">&quot;</span><span class="va">$(</span><span class="ex">getConfigKey</span> <span class="st">&quot;botadmin&quot;</span><span class="va">)</span><span class="st">&quot;</span> <span class="st">&quot;</span><span class="va">$(</span><span class="fu">df</span> -h<span class="va">)</span><span class="st">&quot;</span></a></code></pre></div>
 <p>For more information see <a href="doc/8_custom.md">Expert Use</a></p>
 <h3>Blocked by telegram?</h3>
 <p>This may happen if to many or wrong requests are sent to api.telegram.org, e.g. using a invalid token or not existing API calls. If the block stay for longer time you can ask telegram service to unblock your IP-Adress.</p>
 <p>You can check with curl or wget if you are blocked by Telegram:</p>
-<div class="sourceCode" id="cb6"><pre class="sourceCode bash"><code class="sourceCode bash"><a class="sourceLine" id="cb6-1" title="1"><span class="ex">curl</span> -m 10  https://api.telegram.org/bot</a>
-<a class="sourceLine" id="cb6-2" title="2"><span class="co">#curl: (28) Connection timed out after 10001 milliseconds</span></a>
-<a class="sourceLine" id="cb6-3" title="3"></a>
-<a class="sourceLine" id="cb6-4" title="4"><span class="fu">wget</span> -t 1 -T 10 https://api.telegram.org/bot</a>
-<a class="sourceLine" id="cb6-5" title="5"><span class="co">#Connecting to api.telegram.org (api.telegram.org)|46.38.243.234|:443... failed: Connection timed out.</span></a></code></pre></div>
+<div class="sourceCode" id="cb7"><pre class="sourceCode bash"><code class="sourceCode bash"><a class="sourceLine" id="cb7-1" title="1"><span class="ex">curl</span> -m 10  https://api.telegram.org/bot</a>
+<a class="sourceLine" id="cb7-2" title="2"><span class="co">#curl: (28) Connection timed out after 10001 milliseconds</span></a>
+<a class="sourceLine" id="cb7-3" title="3"></a>
+<a class="sourceLine" id="cb7-4" title="4"><span class="fu">wget</span> -t 1 -T 10 https://api.telegram.org/bot</a>
+<a class="sourceLine" id="cb7-5" title="5"><span class="co">#Connecting to api.telegram.org (api.telegram.org)|46.38.243.234|:443... failed: Connection timed out.</span></a></code></pre></div>
 <p>Since Version 0.96 bashbot offers the option to recover from broken connections (aka blocked). Therefore you can provide a function named <code>bashbotBlockRecover()</code> in <code>mycommands.sh</code>. If the function exists it is called every time when a broken connection is detected.</p>
 <p>Possible actions are: Check if network is working, change IP-Adress or simply wait some time.</p>
 <p>If everything seems OK return 0 for retry or any non 0 value to give up.</p>
-<div class="sourceCode" id="cb7"><pre class="sourceCode bash"><code class="sourceCode bash"><a class="sourceLine" id="cb7-1" title="1"><span class="co"># called when bashbot sedn command failed because we can not connect to telegram</span></a>
-<a class="sourceLine" id="cb7-2" title="2"><span class="co"># return 0 to retry, return non 0 to give up</span></a>
-<a class="sourceLine" id="cb7-3" title="3"><span class="fu">bashbotBlockRecover()</span> <span class="kw">{</span></a>
-<a class="sourceLine" id="cb7-4" title="4">    <span class="co"># place your commands to unblock here, e.g. change IP-Adess or simply wait</span></a>
-<a class="sourceLine" id="cb7-5" title="5">    <span class="fu">sleep</span> 60 <span class="kw">&amp;&amp;</span> <span class="bu">return</span> 0 <span class="co"># may be temporary</span></a>
-<a class="sourceLine" id="cb7-6" title="6">    <span class="bu">return</span> 1 </a>
-<a class="sourceLine" id="cb7-7" title="7">    <span class="kw">}</span></a>
-<a class="sourceLine" id="cb7-8" title="8"></a></code></pre></div>
+<div class="sourceCode" id="cb8"><pre class="sourceCode bash"><code class="sourceCode bash"><a class="sourceLine" id="cb8-1" title="1"><span class="co"># called when bashbot sedn command failed because we can not connect to telegram</span></a>
+<a class="sourceLine" id="cb8-2" title="2"><span class="co"># return 0 to retry, return non 0 to give up</span></a>
+<a class="sourceLine" id="cb8-3" title="3"><span class="fu">bashbotBlockRecover()</span> <span class="kw">{</span></a>
+<a class="sourceLine" id="cb8-4" title="4">    <span class="co"># place your commands to unblock here, e.g. change IP-Adess or simply wait</span></a>
+<a class="sourceLine" id="cb8-5" title="5">    <span class="fu">sleep</span> 60 <span class="kw">&amp;&amp;</span> <span class="bu">return</span> 0 <span class="co"># may be temporary</span></a>
+<a class="sourceLine" id="cb8-6" title="6">    <span class="bu">return</span> 1 </a>
+<a class="sourceLine" id="cb8-7" title="7">    <span class="kw">}</span></a>
+<a class="sourceLine" id="cb8-8" title="8"></a></code></pre></div>
 <p>@Gnadelwartz</p>
 <h2>That's it!</h2>
 <p>If you feel that there's something missing or if you found a bug, feel free to submit a pull request!</p>
-<h4>$$VERSION$$ v1.0-18-g9b3d689</h4>
+<h4>$$VERSION$$ v1.0-21-g6718d24</h4>
 </body>
 </html>
diff --git a/README.md b/README.md
index 25ba00e..91c13b7 100644
--- a/README.md
+++ b/README.md
@@ -18,6 +18,7 @@ More concrete on the common commands provided by recent versions of [coreutils](
 
 *Note for MacOS and BSD Users:* As bashbot heavily uses modern bash and (gnu) grep/sed features, bashbot will not run without installing additional software, see [Install Bashbot](doc/0_install.md)
 
+*Note for emmbedded systems:* busybox or toybox ONLY is not sufficient, you need a to install a "real" bash, see [Install Bashbot](doc/0_install.md)  
 
 Bashbot [Documentation](https://github.com/topkecleon/telegram-bot-bash) and [Downloads](https://github.com/topkecleon/telegram-bot-bash/releases) are available on www.github.com
 
@@ -74,8 +75,11 @@ If you don't want to register for Telegram you should stop reading here ;-)
 After you're registered to Telegram send a message to [@botfather](https://telegram.me/botfather),
 [create a new Telegram Bot token](doc/1_firstbot.md) and write it down. You need the token to install the bot.
 
-Now open a terminal and check if bash is installed: ```which bash && echo "bash installed!"```.
-If you get an error message bash is not installed.
+Now open a terminal and check if bash is installed:
+ ```
+which bash && echo "bash seems available..."
+```
+
 
 Create a new directory, change to it:  ```mkdir tbb; cd tbb``` and download the latest '*.tar.gz' file from
 [https://github.com/topkecleon/telegram-bot-bash/releases](https://github.com/topkecleon/telegram-bot-bash/releases). This can be done with the commands:
@@ -261,4 +265,4 @@ bashbotBlockRecover() {
 
 If you feel that there's something missing or if you found a bug, feel free to submit a pull request!
 
-#### $$VERSION$$ v1.0-18-g9b3d689
+#### $$VERSION$$ v1.0-21-g6718d24
diff --git a/README.txt b/README.txt
index 2310ffa..0e40f21 100644
--- a/README.txt
+++ b/README.txt
@@ -29,6 +29,8 @@ Notes](doc/7_develop.md#common-commands)
 grep/sed features, bashbot will not run without installing additional software, 
 see [Install Bashbot](doc/0_install.md)
 
+*Note for emmbedded systems:* busybox or toybox ONLY is not sufficient, you 
+need a to install a "real" bash, see [Install Bashbot](doc/0_install.md)  
 
 Bashbot [Documentation](https://github.com/topkecleon/telegram-bot-bash) and 
 [Downloads](https://github.com/topkecleon/telegram-bot-bash/releases) are 
@@ -93,9 +95,11 @@ After you're registered to Telegram send a message to
 [create a new Telegram Bot token](doc/1_firstbot.md) and write it down. You 
 need the token to install the bot.
 
-Now open a terminal and check if bash is installed: ```which bash && echo "bash 
-installed!"```.
-If you get an error message bash is not installed.
+Now open a terminal and check if bash is installed:
+ ```
+which bash && echo "bash seems available..."
+```
+
 
 Create a new directory, change to it:  ```mkdir tbb; cd tbb``` and download the 
 latest '*.tar.gz' file from
@@ -351,4 +355,4 @@ wait
 If you feel that there's something missing or if you found a bug, feel free to 
 submit a pull request!
 
-#### $$VERSION$$ v1.0-18-g9b3d689
+#### $$VERSION$$ v1.0-21-g6718d24
diff --git a/bashbot.sh b/bashbot.sh
index a6fc42f..8b93b11 100755
--- a/bashbot.sh
+++ b/bashbot.sh
@@ -11,7 +11,7 @@
 # This file is public domain in the USA and all free countries.
 # Elsewhere, consider it to be WTFPLv2. (wtfpl.net/txt/copying)
 #
-#### $$VERSION$$ v1.0-18-g9b3d689
+#### $$VERSION$$ v1.0-21-g6718d24
 #
 # Exit Codes:
 # - 0 success (hopefully)
@@ -22,8 +22,16 @@
 # - 5 cannot connect to telegram bot
 # - 6 mandatory module not found
 # - 6 can't get bottoken
+# - 10 not bash!
 # shellcheck disable=SC2140,SC2031,SC2120,SC1091
 
+# emmbeded system may claim bash but it is not
+# check for bash like ARRAY handlung
+if ! (unset a; set -A a a; eval "a=(a b)"; eval '[ -n "${a[1]}" ]'; ) > /dev/null 2>&1; then
+	echo "iError: Current shell does not support ARRAY's, may be busbox ash shell. pls install a real bash!";
+	exit 10
+fi
+
 # are we running in a terminal?
 if [ -t 1 ] && [ -n "$TERM" ];  then
     CLEAR='clear'
@@ -34,6 +42,11 @@ if [ -t 1 ] && [ -n "$TERM" ];  then
     NC='\e[0m'
 fi
 
+# we need some bash 4+ features, check for old bash by feature
+if [ "$(echo -e "\u1111")" == "\u1111" ]; then
+	echo -e "${ORANGE}Warning: Unicode '\uxxxx' seems not supported, install a more current bash.${NC}"
+fi
+
 # some important helper functions
 # returns true if command exist
 _exists() {
diff --git a/doc/0_install.md b/doc/0_install.md
index 18fa362..7bc6dc4 100644
--- a/doc/0_install.md
+++ b/doc/0_install.md
@@ -1,5 +1,21 @@
 #### [Home](../README.md)
 
+## Check bash installation
+
+There may be systems where bash seems to be installed but it is not, e.g. emmbedded systems, or the bash version is to old.
+Run the following commands to see if your bash looks ok ...
+
+```bash
+# does the system say bash is there?
+which bash && echo "bash seems available..."
+
+# real bash supports ARRAY
+bash -c 'eval "a=(1)" && echo "Shell supports ARRAY..."'
+
+# check for ok version by feature
+[ "$(echo "\u1111")" == "\u1111" ] && echo "Bash version may to old..."
+```
+
 ## Install bashbot
 
 1. Go to the directory you want to install bashbot, e.g.
@@ -153,5 +169,5 @@ The old format is supported for backward compatibility, but may fail for corner
 
 #### [Next Create Bot](1_firstbot.md)
 
-#### $$VERSION$$ v1.0-20-gc292292
+#### $$VERSION$$ v1.0-21-g6718d24