single quote characters in a single-quoted string in shells
A very quick and simple comment on building single-quoted strings in shell scripts which include single quotes. Note that it’s not possible to include a...
LINES and COLUMNS environment magic
Ever wondered why you can read the $LINES and $COLUMNS environment variables from your text shell and have them seemingly aware (or indeed, actually aware)...
Arctic Death Spiral
The Arctic Death Spiral describes events unfolding such that we have a feedback loop whereby the the increasing amount of ice melting over summer is...
Exception-al perl signals
Scenario For a certain code-base it’s decided it would be useful to be able to trigger an exception on-demand (mid-way through a process working). Why?...
openssl s_client – SNI testing with -servername
When testing network connections to a server using the TLS SNI extension to allow a single IP address to respond with different certificates the openssl...
XTerm*VT100*selectToClipboard: true
The Problem Working with copying text between applications which use the X11 PRIMARY (eg. the quick-copy of selected text and pasting by clicking the middle...
Useful Commands
A list of commands / references I’ve found useful. Also see my old wiki page. stdbuf – Run COMMAND, with modified buffering operations for its...
pip – Cannot fetch index base URL http://pypi.python.org/simple/
You want to use pip to install a module from PyPI. However your server distribution in a little old (at the time of writing this...
bandwidth measurement using iperf
I wrote about using netcat to measure bandwidth between servers which works perfectly well in a minimal sort of way (and in particular between servers...
On the importance of reading the docs – PHP’s date_parse errors
It’s important to read the documentation, and then read it again once or twice. PHP’s date_parse function parses a datetime string and returns an “array with information...