Passing CFLAGS and LDFLAGS to cgo

I was trying to build https://github.com/systemfreund/go-libshout which wraps the C libshout library with Go.  On Linux this worked fine, but on OpenBSD this was a bit more of a challenge as cgo could not find libshout.  (install libshout with pkg_add first)

Although -lshout is specified as an LDFLAG  in the go source code, I needed to to specify the include path for libshout and also link to libspeex (-lsppex)

CFLAGS and LDFLAGS can be passed to go build as environmental variables so I set:

export CGO_CFLAGS='-I/usr/local/include'
export CGO_LDFLAGS='-L/usr/local/lib -lshout -lspeex'

Then I is was able to do

go build -x  github.com/systemfreund/go-libshout

(the -x is very useful for checking was gets passed to cgo)

Ansible ad-hoc commands

Create an inventory file

host1.something
host2.something
[group1]
group1host.something
group2host.something

Run a command on all hosts
ansible -i inventory_file all -m command -a "uptime"

This specifies the inventory file (-i) run on all hosts (all) and run the command module (runs a remote command) with the module argument uptime (-a)

Run a command on all hosts simpler
ansible -i inventory_file all  -a "uptime"

Same as above.  Notice that the module name was not specified as the command module is used by default

Run a command on hosts in group1 with sudo
ansible -i inventory_file group1 -s -K -a "service rsyslog status"

-s Use sudo
-K ask for the sudo password (can be omitted if not required)

Copy a file to all hosts
ansible -i inventory_file all -m copy -a "src=~/.vimrc dest=~"

Real Time Scheduling for audio in openSUSE

I was getting the following message from jack / hydogen
Cannot use real-time scheduling

To solve this I added the following to  /etc/security/limits.conf
@audio - rtprio 99
@audio - memlock 250000
@audio - nice -10

and also added myself to the audio group (sudo usermod -a -G audio jon)

Bulk Filename Rewriting

In zsh you'll find zmv (autoload zmv) and in zmv it's easy to rewrite bulk files.  For example, I had some downloaded files that were something.mp3?id=8795294528 etc and wanted to cut off the cruft at the end.

zmv '(*.mp3)*' '$1'

Strip comments from an XML file

Ever had an xml file bloated with comments? Here's a great one-liner for striping them.

tidy -quiet -asxml -xml -indent -wrap 1024 --hide-comments 1 file.xml

Thanks to http://stackoverflow.com/questions/1464697/stripout-comments-from-xml

Convert pem certificate to pkcs12 / p12

openssl pkcs12 -export -in widgets.crt -inkey widgets.key -out widgets.p12

Multiple desktops with xrandr on fluxbox

I use fluxbox.  Sometimes I work with multiple screens, sometimes I don't, sometimes those screen are various resolutions.

To see what screens I have available I run

xrandr -q

from there I can see what screens and what resolutions I have availble.  Then I can configure my setup with appropriately

e.g
xrandr --output VGA1 --mode 1680x1050 --left-of LVDS1

Thanks to http://awesome.naquadah.org/wiki/Using_Multiple_Screens for this one.