Dave Holland's home page

bash
10:07am, Tuesday 9 May 2006

While reading LWN/linux.com I discovered that bash can do tab-completion on a remote host:

scp foo.txt remotehost:somed<tab>

goes off and makes a batch-mode ssh connection to remotehost, finds the possible completions and returns them to the partial command line. That's just freaky.

Oh, and bind '"\t":menu-complete' gets cyclic-completion instead of partial-completion, which is strange at first but feels like it might be faster when I get used to it.

And all because...
10:52pm, Tuesday 11 April 2006 (Updated 11:46pm, Tuesday 18 April 2006)

...I wanted pretty ping graphs like Russell's. So I had to sit down with the CLI manual for my ADSL router. Turns out the command syntax is sufficiently close to Linux iptables that I figured out

firewall rule create chain=sink index=4 prot=icmp icmptype=echo-request action=accept
firewall rule create chain=source index=4 prot=icmp icmptype=echo-reply action=accept

were the runes I required. Now I have pretty ping graphs too!

Update:

Argh, a new firmware version has changed the command syntax... This seems to work:

service system ifadd name=PING_RESPONDER group=wan

Spam of the day
2:32pm, Wednesday 29 March 2006

Subject: uselessness onslaught

Just about sums it up, really...

Unknown error 990
11:31am, Friday 17 February 2006

In a word: filesystem corruption. (OK, that was two words.) Fortunately xfs_repair does exactly what its name suggests, and "debsums -ca" and "apt-get install --reinstall" appear to have salvaged the worst of the damage.

Compression
10:00am, Thursday 16 February 2006

I just found out about rzip and 7zip, new-ish file compression utilities. Being obsessive about performance and statistics and stuff, I ran a few tests: all these required the compressor to produce its "best" (most compressed) output.

compressor	size of compressed file (%)	CPU time (s)
gzip	48.9	1.38
bzip2	46.1	12.4
rzip	45.2	17.2
7zip	43.1	28.2

So gzip is far, far away the fastest (which explains its continued widespread use) but using one of the others could save significant amounts of space with very large files - if you have the time to spare.