Go enjoy Python3

Given a string, get a truncated string of length up to 12.

The task is ambiguous, as it doesn't say anything about whether or not 12 should include terminating null character or not. None the less, let's see how one would achieve this in various languages.
Let's start with python3

import sys
print(sys.argv[1][:12])

Simple enough, in essence given first argument, print it up to length 12. As an added this also deals with unicode correctly that is if passed arg is 車賈滑豈更串句龜龜契金喇車賈滑豈更串句龜龜契金喇, it will correctly print 車賈滑豈更串句龜龜契金喇. (note these are just random Unicode strings to me, no idea what they stand for).

In C things are slightly more verbose, but in essence, I am going to use strncpy function:

#include <stdio.h>
#include <string.h>
void main(int argc, char *argv[]) {
 char res[12];
 strncpy(res,argv[1],12);
 printf("%s\n",res);
}

This treats things as byte-array instead of unicode, thus for unicode test it will end up printing just 車賈滑豈. But it is still simple enough.
Finally we have Go

package main

import "os"
import "fmt"
import "math"

func main() {
 fmt.Printf("%s\n", os.Args[1][:int(math.Min(12, float64(len(os.Args[1]))))])
}

This similarly treats argument as a byte array, and one needs to cast the argument to a rune to get unicode string handling. But there are quite a few caveats. One cannot take out of bounds slices. Thus a naïve os.Args[1][:12] can result in a runtime panic that slice bounds are out of range. Or if a string is known at compile time, a compile time error. Hence one needs to calculate length, and do a min comparison. And there lies the next caveat, math.Min() is only defined for float64 type, and slice indexes can only be integers and thus we end up writing ]))))])...

12 points for python3, 8 points for C, and Go receives nul points Eurovision style.

EDIT: Andreas Røssland and James Hunt are full of win. Both suggesting fmt.Printf("%.12s\n", os.Args[1]) for go. I like that a lot, as it gives simplicity & readability without compromising the default safety against out of bounds access. Hence the scores are now: 14 points for Go, 12 points for python3 and 8 points for C.

EDIT2: I was pointed out much better C implementation by Keith Thompson - http://pastebin.com/5i7rFmMQ in essence it uses strncat() which has much better null termination semantics. And Ben posted a C implementation which handles wide characters http://www.decadent.org.uk/ben/blog/truncating-a-string-in-c.html. I regret to inform you that this blog post got syndicated onto hacker news and has now become the top viewed post on my blog of all time, overnight. In retrospect, I regret awarding points at the end of the blog post, as that's just was merely an expression of opinion and is highly subjective measure. But this problem statement did originate from me reviewing go code that did "if/then/else" comparison and got it wrong to truncate a string and I thought surely one can just do [:12] which has lead me down the rabbit hole of discovering a lot about Go; it's compile and runtime out of bounds access safeguards; lack of universal Min() function; runes vs strings handling and so on. I'm only a beginner go programmer and I am very sorry for wasting everyone's time on this. I guess people didn't have much to do on a Throwback Thursday.

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