byronc bits

So, pcapy is a great, simple library to interface with libpcap. It works well for reading live packets and dump files. There's only one problem: there is no way to modify or create a struct pcap_header from Python code. So there's really no way to add data to the packets and add them to a dump file.

Yet another command I'll never remember unless I write it down. Here's how to view a certificate. In my case I was viewing a certificate that Mutt had stored:

openssl x509 -in .mutt_certs -noout -text

In honor of the decision to move Python development to Mercurial, I decided to write something helpful. I've found __git_ps1() to be incredibly useful, so, here's my take on _hg_ps1():

_hg_root()
{
    local basedir=$(pwd)

    while [ '/' != "${basedir}" ]; do
        if [ -d "${basedir}/.hg" ]; then
            break;
        fi

        basedir="$(readlink -f "${basedir}/..")"
    done

    [ '/' == "${basedir}" ] || echo -n "${basedir}"
}

_hg_ps1()
{
    local g=$(_hg_root)
    if [ -n "${g}" ]; then
        local branch

        branch=$(hg branch)
        if [ -f "${g}/.hg/bookmarks.current" ]; then
            branch="$(< "${g}/.hg/bookmarks.current"):${branch}"
        fi

        if [ -n "${1-}" ]; then
            printf "$1" "${branch}"
        else
            printf " (%s)" "${branch}"
        fi
    fi
}

Yes, I know that the hg root command does the same thing as my _hg_root(), but it felt slow running mercurial before printing each prompt. The only thing that's missing is showing when merges are in progress. I'll try to add that the next time I need to do a manual merge.

Update: It seems that some of my repositories don't have a .hg/branch file so I'm calling hg branch for that info. Also, the readlink line in _hg_root() did not properly handle spaces.

I use ViM macros (aka complex-repeat) all the time. Occasionally, I find that it would be nice to reuse one of my macros across editing sessions. Turns out it's pretty easy to save the macro. Just add a line like the following to a file that gets sourced when your file is opened by ViM (This example is from ~/.vim/ftplugin/rst.vim).

let @h = "yypVr"

Now, whenever I open a ReStructured Text file, I can hit @h and my macro will run.

GNU tar provides the -S option to efficiently handle sparse files. Of course it only works if you create the tarball with the -S option. That is all.