Author: ryan

Set your Raspberry Pi up for Wifi roaming
I’ve had a Raspberry Pi 2 just sitting around for several months, waiting for a purpose. Since I haven’t come up with a purpose, I decided to make it a portable headless Linux box that will travel with me, connect to Wifi automatically, and eventually, hopefully, set it up as a Piratebox. First things first, lets get it connecting.

It was easier than I thought it was going to be to set it to automatically connect. Basically, I modified /etc/network/interfaces to add a roam configuration for wpa supplicant.
```
# Include files from /etc/network/interfaces.d:
source-directory /etc/network/interfaces.d

auto lo
iface lo inet loopback

iface eth0 inet manual

allow-hotplug wlan0
iface wlan0 inet manual
    # wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
    wpa-roam /etc/wpa_supplicant/wpa_roam.conf

allow-hotplug wlan1
iface wlan1 inet manual
    #wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
    wpa-roam /etc/wpa_supplicant/wpa_roam.conf
```
I just added the two lines that start with wpa-roam and commented out the default wpa_supplicant.conf lines. Next up was to create the /etc/wpa_supplicant/wpa_roam.conf file:
```
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1
network={
        ssid="home"
        key_mgmt=NONE
}
network={
        ssid="iPhoneHotSpot"
        key_mgmt=WPA-PSK
        psk="PASSWORD"
}
```
Adjust the parameters for your networks. Plugging the Pi into the network and manually running sudo ifdown wlan0;sudo ifup wlan0 is how I tested it.

Finally, the pi needs to see if it doesn’t have a network connection, and if it doesn’t, bring wlan0 and then back up and see if it will connect. My wifi dongle (the Edimax EW-7811Un) is on wlan0, so you may need to modify. I set a crontab (sudo crontab -e) with the following line:
```
* * * * * /bin/ping -q -c2 8.8.8.8 || (/sbin/ifdown --force wlan0 ;/sbin/ifup wlan0 )
```
Every minute the Pi will send out two pings to Google’s DNS servers, and if it doesn’t get a reply, it will take the connection down and bring it back up. Now I have a Pi that will autoconnect to wifi.
January 27, 2016
Fixing my .taskpaper reset alias for bash
There was a little problem with my alias to reset a .taskpaper list by removing all of the @dones. It didn’t remove any spaces before the @done, so each line would gain a space every day. This fixes it:
```
alias rst="sed -i '' 's/ *@done$.*$//g'"
```
Now it removes one or more spaces that could be before @done.
January 26, 2016

Switching terminals in tmux with ALT-numbers

I’m a big tmux fan, switching from screen a few years ago. Lately, I’ve been working on ways to switch between terminals faster. Now I’m using the ALT (Option key actually) under OS X to switch between the different terminals. The switching starts with the backtick and goes across the upper row of the keyboard until the equal key for 12 terminals, and then continues on with the second row and the Q key up until the I key for terminal 20. It seems to be working pretty well, the biggest issue is that I can’t jump to specific buffers in Weechat with ALT-BUFFER#, but that’s not a big deal (I’m using ALT-J BUFFER# right now.) Here’s the specific section of my .tmux.conf file:

# Use ALT-n keys to select pane
bind-key -n M-"`" select-window -t 0
bind-key -n M-1 select-window -t 1
bind-key -n M-2 select-window -t 2
bind-key -n M-3 select-window -t 3
bind-key -n M-4 select-window -t 4
bind-key -n M-5 select-window -t 5
bind-key -n M-6 select-window -t 6
bind-key -n M-7 select-window -t 7
bind-key -n M-8 select-window -t 8
bind-key -n M-9 select-window -t 9
bind-key -n M-0 select-window -t 10
bind-key -n M-- select-window -t 11
bind-key -n M-= select-window -t 12

bind-key -n M-q select-window -t 13
bind-key -n M-w select-window -t 14
bind-key -n M-e select-window -t 15
bind-key -n M-r select-window -t 16
bind-key -n M-t select-window -t 17
bind-key -n M-y select-window -t 18
bind-key -n M-u select-window -t 19
bind-key -n M-i select-window -t 20

January 25, 2016

Working with Taskpaper files in vim

I’ve been experimenting with Taskpaper for lists over the last couple of weeks, and really like the flexibility. All of my lists are stored as text files in Dropbox, which makes it easy to use/update lists from anything or anywhere. On my iPhone I use Drafts to quickly add to the task lists and Editorial to work with the tasks.

On the desktop and laptop, I’ve settled upon using vim. Davidoc/taskpaper.vim gives me all sorts of neat ways of dealing with .taskpaper files, and has been working pretty well so far.

January 25, 2016
Using a Here Document with bash and MySQL
This past week I worked on a bash script to create some input files from a MySQL database. My problem was trying to use multiple line MySQL statements, which was messing everything up. The solution was to use bash’s Here Documents. It’s a way to direct lines into a command. For me, the command looked like this:
```
mysql DBNAME <<EOF
SELECT *
FROM table
WHERE item = 'WhatIWant'
EOF
```
Everything between the two EOF would be submitted to MySQL. The next problem was that bash was trying to still interpret the MySQL statement which had backticks in it. To solve this issue, I learned that I needed to enclose the first EOF in quotes.
```
mysql DBNAME <<"EOF"
```
Bash then left my MySQL command alone, and all was right in the world.
January 24, 2016
Resetting a daily taskpaper list
I have a couple daily taskpaper lists that by the end of the have an @done on each line and I need to reset it for the next day. Instead of trying to do a search and replace everyday, I added a bash alias to .bash_profile (or .bashrc):
```
alias rst="sed -i '' 's/@done$.*$//g'"
```
The extra '' after the -i is because OS X’s sed requires an extension for backups. Set it to nothing and OS X won’t create backups.
January 22, 2016
Saving bash shell history for multiple shells
The history from the commands typed into bash are very useful from time to time, especially when I think “Oh, I’ll remember that command next time I need it”, and then I don’t. The problem with bash’s history are twofold:
- It only saves history when the terminal exits cleanly, so if your connection drops or you have to kill the current process, you lose your history.
- If you are running multiple terminals, or using a terminal multiplexer like tmux (my favorite!) or screen, the last bash to exit overwrites any other history with its history.
So, after a little searching I’ve found a solution that works for me for now.
```
# Save history
#Set history suffix to the current terminal
HISTSUFFIX=`tty | sed 's/\///g;s/^dev//g'`
# All terminals' histories will be stored in separate files
# in .bash_history_log. That folder will need to be created.
HISTFILE="$HOME/.bash_history_log/bash_history_$HISTSUFFIX"
# Time stamp the commands in the history file
HISTTIMEFORMAT="%y-%m-%d %H:%M:%S "
# Don't save duplicate commands
HISTCONTROL=ignoredups:ignorespace
# Control the size of the file
HISTSIZE=1000
HISTFILESIZE=5000
# Bash will append to the history file
shopt -s histappend
# Bash will append to the history file after each time
# the prompt is shown. This way it's always saved.
PROMPT_COMMAND='history -a'
```
Put that in your .bashrc and you’re good to go. Comments are welcome!
January 21, 2016
Markdown to presentation
Since my preferred interface is the command line, yesterday I was thinking how cool it would be to knock out a presentation from Markdown. I could work on the content, and not get distracted by the interface. Luckily, I didn’t have to look any further than Pandoc. Pandoc can take a multitude of formats and convert to other formats. For example, to create a presentation from a Markdown file, a simple pandoc -t revealjs -s presentation.markdown -o presentation.html.

Before the presentation is viewable, you need to download the reveal.js framework. Unzip it and rename the folder to reveal.js and put it in the same place as the html file created by Pandoc. You can then open the html file up in your browser and present away! The easiest way to publish the presentation publicly would probably be in Dropbox. Share the link to the html publicly and you should be good to go (your mileage may vary, I haven’t tested this yet).

The format of the Markdown folder is pretty simple:
```
% My Great Presentation
% By Ryan Collins

# Slide 1

This is the content for slide one.

. . .

Three dots with spaces between them will pause the presentation.

## Slide 1a

A header 2 will navigate *down* from the previous slide.

# Slide 2

Another header 1 will navigate *right*

# Slide 3

> - List item 1
> - List item 2
```
Pandoc will create a title slide from the % lines above automatically. You can also include graphics with the standard Markdown ![My great graphic](link/to/graphic.png). I’m going to play around with it more, and I also hope to find time to check out the other html5 presentation formats that pandoc works with, including DZSlides, Slidy, Slideous, and S5.
January 20, 2016
Jumping to multiple hosts with ssh behind a gateway
At home I have several hosts that I need to ssh into at various times. Unfortunately, since IPv6 is widely deployed, I am stuck sshing into one host that is publically accessible, and from there sshing into other hosts. Cumbersome to say the least, but it does look cool when I’m showing it off.

Anyway, you can automate the connection with netcat on the gateway host. I like to put my ssh commands into my ~/.ssh/config file so then I don’t have to remember anything. To jump to an internal host from the gateway I add the following to my ~/.ssh/config file on the client (most notably, my 2010 MacBook Pro).
```
Host macmini
    hostname LOCALIP
    user gadmin
    ProxyCommand ssh USER@GATEWAY nc %h %p
```
Replace LOCALIP with the address of the host to which you want to jump, and replace USER@GATEWAY with the gateway’s username and address. You can use other hosts defined in your ~/.ssh/config file, so if you have a host for GATEWAY, you can use it.
January 19, 2016
Resetting a .taskpaper file
I use a couple of .taskpaper files for checklists of things that need to be done every day. In it, after a task is completed the task gets an @done tag added. But the next day I want to start fresh. I could do a find/replace, but sed at the command line works better:
```
alias rst="sed -i 's/@done$.*$//'"
```
Adding the above alias to my ~/.bash_profile adds the ability to reset a taskpaper file with a simple rst FILE.taskpaper. Under OS X, the -i parameter requires an extension for a backup file. You can simply have ” to set it to nothing and then a back up file won’t be created.
January 19, 2016