Misc on Miek Gieben

Source Code Pro

Thu, 27 Sep 2012 19:44:00 +0000

Indeed a really nice font and fully open source. Using it now at 11pt. See:

Sync subversion to github.com

Wed, 27 Jun 2012 08:26:00 +0000

This is a post that details on how to sync a subversion repository to git repository on github.com, and how to keep it in sync.

The following sites were instrumental in getting this to work:

There are a number of steps to take. From a bird’s eye view:

Use git svn to clone the svn repo to a git repo;
Create a github git repo;
Add a remote origin in your local git to the remote github repo;
Use some SSH foo to use a separate SSH key for pushing to github.com.

Prerequisites

We are working with the fictional svn repo located at https://svn.example.net/example;
git-svn is installed;
ssh is installed.

Clone the repository

Pandoc to RFC

Wed, 28 Sep 2011 13:45:00 +0000

This is an follow-up on this pandoc item in Dutch.

When writing RFC 4641 we directly wrote the XML. Needless to say is was kinda tedious even thought the XML of xml2rfc is very “light”.

Nowadays I’m a fan of the markdown syntax and especially the syntax as supported (created?) by Pandoc.

So for my next RFC (if ever!) I decided I wanted to use Pandoc. As xml2rfc uses XML I thought the easiest way would be to create docbook XML and transform that using XSLT.

Computer Languages

Sun, 01 Aug 2010 19:17:00 +0000

I have done programming in (or at least looked at) the following computer languages during my live. Of course the world is not a perfect place, but some languages out there are just plain awful.

BASIC - with line numbers! At the time (I was 11) didn’t know there was something else out there. Fun and easy language, although I never programmed in it ever again.
Pascal - After BASIC, there is no going back to Pascal. Only briefly looked at it in my youth and discarded it in favor for BASIC…

Prime sieve (in Go ofcourse)

Tue, 24 Nov 2009 22:55:00 +0000

After reading up on the prime sieve, and playing with Go for the past week I thought needed to implement this algorithm in Go and make it parallel.

I want to create a set (n in 2..N) goroutines. Each of these routines will check if it can divide a number (i) by n (integer division). If so the number i is not prime, otherwise it is given to the next goroutine. Communication between the goroutines is done via channels as in this example.

More Go

Mon, 23 Nov 2009 22:45:00 +0000

Still learning and playing with Go, I’ve rewritten my cat experiment, to use a *bufio.Reader, which is more correct I think. I’m also slowly wrapping my mind around the concept of Interfaces. As a non-OO programmer (C and non-OO Perl) is starting to see why this is useful.

So today’s exercises:

Write a cat implementation in Go. See below.
Write a grep implementation in Go. See below.

Cat in go

package main

// A implementation of cat in Go

import (
    "os";
    "fmt";
    "bufio";
    "flag";
)

var numberFlag = flag.Bool("n", false, "number each line")

func cat(r *bufio.Reader) bool {
    i := 1;
    for {
	    buf, e := r.ReadBytes('\n');
	    if e == os.EOF {
		    break
	    }
	    if *numberFlag {
		    fmt.Fprintf(os.Stdout, "%5d  %s", i, buf);
		    i++
	    } else {
		    fmt.Fprintf(os.Stdout, "%s", buf)
	    }
    }
    return true;
}

func main() {
    flag.Parse();
    if flag.NArg() == 0 {
	    cat(bufio.NewReader(os.Stdin))
    }
    for i := 0; i < flag.NArg(); i++ {
	    f, e := os.Open(flag.Arg(i), os.O_RDONLY, 0);
	    if e != nil {
		    fmt.Fprintf(os.Stderr, "%s: error reading from %s: %s\n",
			    os.Args[0], flag.Arg(i), e.String());
		    continue;
	    }
	    if !cat(bufio.NewReader(f)) {
		    os.Exit(1)
	    }
    }
}

Grep in go

package main

// A implementation of Unix grep in Go
// TODO(mg) better error handling

import (
    "os";
    "fmt";
    "bufio";
    "regexp";
    "flag";
)

var numberFlag = flag.Bool("n", false, "number each line")
var filenameFlag = flag.Bool("l", false, "print names of matching files")

func grep(r *bufio.Reader, reg string) (match bool) {
    i := 0;
    for {
	    buf, e := r.ReadBytes('\n');
	    i++;
	    if e == os.EOF {
		    break
	    }
	    if m, _ := regexp.Match(reg, buf); m == true {
		    match = true;
		    if *filenameFlag {
			    return match
		    }
		    if *numberFlag {
			    fmt.Fprintf(os.Stdout, "%5.d:  %s", i, buf)
		    } else {
			    fmt.Fprintf(os.Stdout, "%s", buf)
		    }
	    }
    }
    return match;
}

func main() {
    flag.Parse();
    if flag.NArg() < 1 {
	    fmt.Fprintf(os.Stderr, "%s: missing regexp\n", os.Args[0]);
	    os.Exit(1);
    }
    if flag.NArg() == 1 {
	    if grep(bufio.NewReader(os.Stdin), flag.Arg(0)) {
		    if *filenameFlag {
			    fmt.Fprintf(os.Stdout, "(standard input)\n");
		    }
	    }
    }
    for i := 1; i < flag.NArg(); i++ {
	    f, e := os.Open(flag.Arg(i), os.O_RDONLY, 0);
	    if e != nil {
		    fmt.Fprintf(os.Stderr, "%s: error reading from %s: %s\n",
			    os.Args[0], flag.Arg(i), e.String());
		    continue;
	    }
	    if grep(bufio.NewReader(f), flag.Arg(0)) {
		    if *filenameFlag {
			    fmt.Fprintf(os.Stdout, "%s\n", flag.Arg(i))
		    }
	    }
    }
}

cat in Go

Wed, 18 Nov 2009 19:57:00 +0000

After spending every free minute to Go I’m starting to get a feel for the language. Every one has to start somewhere, so I decided to “port” Unix utils to Go. I’m starting with cat, and thanks to the Go tutorial this is the result.

package main

// An implementation of Unix cat in Go

import (
    "os";
    "fmt";
    "flag";
)

func cat(filename string) bool {
    const NBUF = 512;
    var buf [NBUF]byte;
    if f, e := os.Open(filename, os.O_RDONLY, 0); e != nil {
	    fmt.Fprintf(os.Stderr, "cat: error reading from %s: %s\n",
		    filename, e.String());
	    return true;
    } else {
	    for {
		    switch nr, _ := f.Read(&buf); true {
		    case nr < 0:
			    os.Exit(1)
		    case nr == 0:	// EOF
			    return true
		    case nr > 0:
			    if nw, ew := os.Stdout.Write(buf[0:nr]); nw != nr {
				    fmt.Fprintf(os.Stderr,
					    "cat: error writing from %s: %s\n",
					    filename, ew.String());
				    return false;
			    }
		    }
	    }
    }
    return true;
}

func main() {
    flag.Parse();	// implement -n TODO
    if flag.NArg() == 0 {
	    cat("/dev/stdin")
    }
    for i := 0; i < flag.NArg(); i++ {
	    if !cat(flag.Arg(i)) {
		    os.Exit(1)
	    }
    }
}

In something like 50 lines you have a cat program. I’m really starting to like Go. Next up: extra features and a grep command.

First steps with Go

Mon, 16 Nov 2009 22:43:00 +0000

I joined the go-nuts mailing list a few days ago and it really feels good to receive 200+ emails per day again. Just like in the good old days before good spam filtering (and anti-spam laws).

I also re-watched the presentation Rob Pike gave for Google Tech Talks on youtube.com. In there he presented the following program chain.go: (Formatted with gofmt as it should)

package main

import (
    "flag";
    "fmt";
)

var ngoroutine = flag.Int("n", 100000, "how may")

func f(left, right chan int)    { left <- 1+<-right }

func main() {
    flag.Parse();
    leftmost := make(chan int);

    var left, right chan int = nil, leftmost;
    for i := 0; i < *ngoroutine; i++ {
	    left, right = right, make(chan int);
	    go f(left, right);
    }
    right <- 0;             // bang!
    x := <-leftmost;        // wait for completion
    fmt.Println(x);         // 100000
}

In this short program we make a chain of 100000 goroutines which are connected to each other. Each one adds 1 to the value it gets from its right neighbor. We start it of by giving the last one (right) a value of 0. Then we wait until they are finished and print it.

Go language

Fri, 13 Nov 2009 15:08:00 +0000

I’ve been wanting to learn (and do something) with the language Erlang for over two years now. But every time I fire up vim and start typing a get a this-is-not-Unix feeling (aka Java-sickness). The syntax is just not right for me.

But now Google, by the creators of Unix and C, give us Go! Which promises to give us Erlang functionality in a C-like language. Just what I wanted!

Basically just follow the steps on golang.org. In short it boils down to:

gitvi (update)

Mon, 02 Feb 2009 22:14:00 +0000

A colleague of mine had some nice improvements to gitvi.

Right now gitvi can be edited by itself, because the magic sequence $Hash$ is escaped like this

sed -i -e 's/\$[H]ash:.*\$/$H''ash$/' "$base"

(This was Ton’s idea)

Some other improvements like a -m MSG switch which allows you to enter a commit message for all files you are editing.

And of course it then also needs to have a -h switch.

check if a directory is empty in bash

Sat, 19 Apr 2008 10:20:00 +0000

I had this small problem, how to you check if a directory is empty in the shell? Suppose I want to do

cmd po/*

this fails, if the po directory is empty, which in turn makes my compile barf, but that is another story. I needed something to would check the emptiness of the directory, and if it is not empty perform the command, otherwise it skip it.

The trick here is to remember that if a shell wildcard can not be expanded it will be left alone. So an unexpanded * will stay a *.