Making zsh history conditional on command success

April 7th, 2019

So I thought it would be useful to exclude failed commands from my on-disk zsh history, while still having them available in the in-memory history until the current shell exits. This means that when you’re trying to find the one magic incantation that works of some esoteric command that you haven’t used for years, you can just search for it in your history without fear of repeating old mistakes.

From my .zshrc:


# called before a history line is saved.  See zshmisc(1).
function zshaddhistory() {
  # Prevent the command from being written to history before it's
  # executed; save it to LASTHIST instead.  Write it to history
  # in precmd.
  LASTHIST=$1
  # Return value 2: "... the history line will be saved on the internal
  # history list, but not written to the history file".
  return 2
}

# zsh hook called before the prompt is printed.  See zshmisc(1).
function precmd() {
  # Write the last command if successful, using the history buffered by
  # zshaddhistory().
  if [[ $? == 0 && -n $LASTHIST && -n $HISTFILE ]] ; then
    print -sr -- ${=${LASTHIST%%$'\n'}}
  fi
}

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Connecting to NBN HFC with a linux router

April 7th, 2019

Internode recently migrated me from an ADSL connection to an NBN HFC connection. Here’s how I configured the connection using my own Debian GNU/Linux router instead of the TP-Link VR1600v internode supplies…

NBN Co supplies an Arris CM8200 NTD, which is a modem that bridges local ethernet to the ISP via DOCSIS over the coaxial cable.

Additionally, Internode’s configuration requires PPPoE encapsulation with 802.1q VLAN tagging.

I’m using physical interface eth1, so in /etc/network/interfaces I have:

# See interfaces(5)
auto eth1
iface eth1 inet static
    address 192.168.1.2/24

# VLAN ID 2 for Internode's NBN HFC.
auto eth1.2
iface eth1.2 inet manual

auto nbn
iface nbn inet ppp
    pre-up /bin/ip link set eth1.2 up
    provider nbn

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Window titles in screen and urxvt, from vim

August 15th, 2011

I previously posted about generating title escapes for screen and rxvt-unicode from zsh. I’ve since worked on getting a consistent title from vim, too. It’s become complex enough that I’m spinning it out into a new post.

To set both titles from vim, use its termcap-title options to push the title to screen using the iconstring. When not running under screen, the right titlestring escapes will be inferred from terminfo.

set title
auto BufEnter * let &titlestring = s:MyTitle()

if &term =~ 'screen\(\.\(xterm\|rxvt\)\(-\(256\)\?color\)\?\)\?'
  " Set the screen title using the vim "iconstring"."
  set t_IS=^[k
  set t_IE=^[\
  set icon
  auto BufEnter * let &iconstring = &titlestring
  " Set the xterm title using the vim "titlestring"."
  set t_ts=^[]2;
  set t_fs=^G
endif

where the underlined characters are actual escapes input with ^V, not with literal carets.

As for generating a fancy title string like vim: there are some gotchas. The biggest is that vim does not preserve logical directory names, so getcwd() will resolve symlinks, leading to a different location string than generated by zsh’s %~. Rather than call pwd -L, we might as well unify the expansion syntax and call zsh. Of course, it’s nice to have a fallback, too:

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Disabling hyphen substitution in Adium

June 22nd, 2011

By default Adium replaces two hyphens with an em-dash in text you type or paste. This leads to subtly confusing behaviour when pasting commands:

foo --bar

becomes “foo —bar”, which can look very similar to foo --bar if your contact is using a terminal that supports variable-width glyphs for exotic character points.

It’s a quick fix: stop double-hyphens being transformed to a long dash by right clicking the Adium input field, and unticking Substitutions > Smart Dashes from the menu.