<p>Hello <a href="/r/golang" rel="nofollow">/r/golang</a>,</p>
<p>I'm learning Golang and my current project is to read a UFW log file and display the source IP address and the destination port number. The problem is that I get the following error:</p>
<pre><code>panic: runtime error: index out of range
goroutine 5 [running]:
panic(0x5231e0, 0xc820010140)
/usr/lib/go-1.6/src/runtime/panic.go:481 +0x3e6
main.countIps(0xc82002e020, 0xc820014300, 0xc8200103f0)
/home/ruben/Programming/Golang/src/github.com/J0holo/ufwLogReader/ufwLogReader.go:65 +0x290
created by main.main
/home/ruben/Programming/Golang/src/github.com/J0holo/ufwLogReader/ufwLogReader.go:41 +0x2e4
</code></pre>
<p>The debugger shows that it only occurs after a couple of hundred loops in countIps(), so it's not instantly. The debugger only spits out a assembly file
and in the debugger screen a list of IPs and port numbers that it has found.</p>
<p><a href="https://gist.github.com/j0holo/d3ab4c33cd33305acd20e99f24d04029" rel="nofollow">The source code</a> which also contains an example of a line of an UFW log file.</p>
<p>I already checked if the maps should be accessed by-reference but <a href="http://stackoverflow.com/a/28384528" rel="nofollow">they seem to work like arrays</a> in C. I have no idea how to fix this error with my limited Go knowledge. Plz help, thanks!</p>
<p>EDIT: <a href="/u/the_jester" rel="nofollow">/u/the_jester</a> and <a href="/u/hipone" rel="nofollow">/u/hipone</a> just told me to RTFM. Ty guys.
TIL: "" != nil in Go</p>
<hr/>**评论：**<br/><br/>the_jester: <pre><p>Note that <a href="https://golang.org/pkg/regexp/#Regexp.FindStringSubmatch" rel="nofollow">FindStringSubmatch can return nil</a>, but you reference its return value without checking for nil on line 66.</p></pre>j0holo: <pre><p>Doh, I compared it as a string not as a string array. Just tested it in the go playground.</p>
<p>Will test it tommorow in my program, thanks anyway.</p></pre>hipone: <pre><blockquote>
<p><a href="https://golang.org/pkg/regexp/#Regexp.FindStringSubmatch" rel="nofollow">https://golang.org/pkg/regexp/#Regexp.FindStringSubmatch</a></p>
<p>A return value of nil indicates no match.</p>
</blockquote>
<p>And you don't check for nil <a href="https://gist.github.com/j0holo/d3ab4c33cd33305acd20e99f24d04029#file-ufwlogreader-go-L65" rel="nofollow">here</a>.</p></pre>breml: <pre><p>Maps in go are not concurrency safe. As you access ipCounds and portCounts from go routines, you should protect your access to thous maps.
Edited: The go race detector could help you to localize the race condition.</p></pre>j0holo: <pre><p>Already fixed that problem, the code is now on <a href="https://github.com/j0holo/ufwLogReader" rel="nofollow">github</a>.</p></pre>
