I run Linux at home, and use it constantly at work. On the those few occasions then I have to work on a Windows box I use Cygwin (a unix-like shell for Windows(TM)).

Note: This are also includes web-related things, such as Apache, which arn't really specific to unix & linux systems

• Recovering my lost data: LVM and RAID — Recovering my LVM volume stored on my RAID array.
• Adobe Flash Player in Ubuntu — Getting fullscreen performance out of Adobe Flash under Ubuntu
• My Perfect X11 setup — Portrait PC monitor with compiz + HDTV without compiz
• Logitech Marble Mouse scroll-wheel emulation — How to configure a trackball mouse with extra button to pretend it has a scroll-wheel
• Enabling 256 colour text in terminals — Guide on how to get gnome-terminal/PuTTY + GNU screen + Vim to work in 256-colour mode
• XBMC Media Center (on Ubuntu) — Workarounds and scripts for using XBOX Media Center on Linux
• Using Unison with DokuWiki
• Webmastering — My personal tips and experiences with being a webmaster
• Linux Gateway — Easy-to-use firewall/NAT script I created and similar efforts
• Rob's Personal Debian Etch Notes — Notes for my own benefit about how I've installed Debian at home
• USB Booting — Wanted to reflash my BIOS, without resorting to floppies or CD-ROMs.

Use https://pypi.org/project/duplicity/

I use Cygwin so much, that I need to keep some tips on it here.

• Clipboard fix for Cygwin/X — Fixing up the clipboard in the Cygwin/X Xserver.

(find -mindepth 2 -maxdepth 2 | grep UNWANTED_FILE_NAME | cut -d/ -f2; command ls) | sort | uniq -u

This creates to output streams, one from the find command and one from ls, that are combined, sorted and finally filtered to remove any entries that occurs more than one.

The streams are combined by the parenthesis which create a sub-shell.

find . -type d \( -name .snapshot -prune -o -name .git \)

Looking in the current directory, ., find entries of type d (directories) for which: if the name is snapshot remove it from consideration, if the name is .git carry on (to implicitly -print the entries to STDOUT).

There is actually a rename command, which can be used to change extensions thus:

rename .rpmnew '' *.rpmnew

This would perform the following:

main.cf.rpmnew -> main.cf
master.cf.rpmnew -> master.cf

(Explained to me by The Definitive Guide to Bash Command Line History)

If you want to reuse the arguments from your last command, you can do so like so:

svn status file1 file2 file3
svn diff !!:2  # Equivalent to "svn diff file1 file2 file3"

So that's an “event designator” of !! to select the previous command, coupled with a “word designator” of 2 to select arguments 2 onwards (zero indexed, of course). These are separated by a colon.

Add this function to your BASH environment (e.g. copy'n'paste it to your ~/.bash_profile), and you will be able to make STDERR output from your commands appear red, making them easier to see.

# Red STDERR
# rse <command string>
function rse()
{
	# We need to wrap each phrase of the command in quotes to preserve arguments that contain whitespace
	# Execute the command, swap STDOUT and STDERR, colour STDOUT, swap back
	((eval $(for phrase in "$@"; do echo -n "'$phrase' "; done)) 3>&1 1>&2 2>&3 | sed -e "s/^\(.*\)$/$(echo -en \\033)[31;1m\1$(echo -en \\033)[0m/") 3>&1 1>&2 2>&3
}

Typical usage is as simple as placing the characters “rse ” infront of the command you want to affect the output of.

Suppose you have a script called rse_test.sh:

echo STDOUT
echo STDERR >&2

you would colour its output like so:

rse ./rse_test.sh

and see

STDOUT
STDERR

However, the following does not colour the output:

rse echo ERROR >&2

“ERROR” will be printed in the usual colour, because the redirection directive is intepreted by the shell, and not by the “rse” function. Adding parenthesis would group the commands like so:

( rse ( echo ERROR ) ) >&2

rse wraps all lines send to STDERR with control characters which mean “set foreground colour to red” and “restore default foreground colour”.

The control characters are ANSI escape code sequences which most¹⁾ modern terminals understand.

The escape sequences in the code are:

^[[31;1m -- Set foreground to red (32), set bold (1)
^[[0m    -- Restore default style

In my ~/.bash_profile I have raw ESC characters, but these cannot be (reliably)²⁾ displayed in browsers. So, as a work-around, I have used command-substitution in the code above.

The following text is replaced with an ESC character when it is evalutated by BASH:

$(echo -en \\033)

The “-e” passed to echo tells it to evaluate the text it will be echo'ing, in this case meaning that “\\033” becomes a single character with octal value 33; the ESC char. The “-n” stops echo printing a newline.

Wrapping lines is achieved by using the sed command:

sed -e "s/^\(.*\)$/$(echo -en \\033)[31;1m\1$(echo -en \\033)[0m/"

We provide a sed-script on the command line and ask sed to evaluate it with the “-e” option. The script is a single substitute command, of the form: “s/before/after/”.

Our “before” patterns is a match of the entire line: “^.*$” where we capture the line using escaped-parenthesis: “^\(.*\)$”.

Our “after” pattern is essentially: “{RED}\1{NORMAL}” where “\1” is the text that was captured. RED and NORMAL are as described above when explaining ANSI escape code sequences.

Every process has three file-handles by default:

If you are running only a single program, then the distinction between STDOUT and STDERR is arbitrary - they will both appear on your screen. They become significant when you have a pipe-line of programs.

For example, suppose you want to know how many files are in the directory tree under your current directory. You can list all the files using the “find” command, and you will output something like this:

find: ./ssl/private: Permission denied
find: ./cups/ssl: Permission denied
find: ./vpnc: Permission denied
.
./acpi
./acpi/ac.d
./acpi/ac.d/85-anacron.sh
./acpi/ac.d/cpufreq.sh
./acpi/ac.d/hal-disable-polling.sh
./acpi/ac.d/mount-noatime.sh
./acpi/ac.d/vm-dirty-writeback.sh
./acpi/ac.d/wired-enable-auto-negoatiation.sh
./acpi/ac.d/wireless_set_power.sh
  ...

And you can count the number of lines printed with the word-count utility by specifying the “-l” option for lines: “wc -l”.

Putting these together we get “find | wc -l”, where the output from “find” will be sent as input to “wc -l”. When I run this I get:

find: ./ssl/private: Permission denied
find: ./cups/ssl: Permission denied
find: ./vpnc: Permission denied
2636

Note that the errors from “find” are still displayed, but so is a line-count from “wc”. This is because the errors were printed on STDERR, which is not sent to “wc” as input.

When two programs are piped together, STDOUT is connected to STDIN. STDERR, on the other hand, remains connected to the parent process, which is our shell in this case. Therefore error messages are not processed by the pipe-line. In our example this was useful, we ended up counting the number of files which we have access to. If error messages were printed to STDOUT, then our count-number would be inaccurate.

How is this relevant? Well, it is not possible to manipulate STDERR in a pipeline, so an alternative approach was required.

Although you cannot manipulate STDERR, you can ask your shell to redirect it. The most common use of this is to suppress errors by redirecting them to /dev/null. However, you can do more than redirect them to files.

rse works by swapping STDOUT and STDERR, modifying the new STDOUT, and then swapping them back. This is achieved by nesting subshells, and having each subshell instruct its parent to swap the streams:

( ( {USER-CMD} ) 3>&1 1>&2 2>&3 | {MODIFY-NEW-STDOUT} ) 3>&1 1>&2 2>&3

Where “3>&1 1>&2 2>&3” instructs the parent to swap STDOUT/STDERR. This is parsed from right-to-left, and uses the numbers in the table above. This works by shifting both STDOUT/STDERR up by one number and then moving the top-most one to the bottom; effectively a swap. Therefore it reads: “Renumber STDERR as #3, Renumber STDOUT as STDERR, Renumber #3 as STDOUT”.

Note that each redirection directive appears after a closing parenthesis. Commands listed within parenthesis are executed in a new sub-shell, and therefore a parent-child relationship is created. This allows us to instruct the parent to manipulate the child's output streams.

In order for all this magic to work, the user's command must be run in the deepest sub-shell. This is achieved by re-assembling the arguments passed to the rse() function into a command-line and then executing them.

eval $(for phrase in "$@"; do echo -n "'$phrase' "; done)

“eval” is a BASH built-in which executes a (single) string passed to in the same way which command you enter at the prompt are.

“$@” is the original list of arguments passed to the function. The code iterates over it and stitched them togther so that eval has a single command strint to execute.

echo "Hello" "World" "How are you?"

If you ever accidently press ^S when using PuTTY, you'll know that this causes it to stop responding, which I need not mention is highly annoying, but I will because it's that annoying .

To get your session to respond again hit Ctrl + Q.

Quoted from http://www.plug.org/pipermail/plug/2004-April/005872.html

Every time I accidentally press Ctrl+s in Putty when connected to any
Linux box via ssh, my session stops responding. How do I restore it?

This is software flow control - left over from the days of serial
connections. Control+S sends XOFF and Control+Q sends XON and together they
make XON/XOFF, or “software,” flow control. Hardware flow control is known
as RTS/CTS and involves switching the signal on a couple of the pins
connected to the serial port.

To disable flow control add this to your shell's init script (e.g. .bashrc):

# Disable software flow control (XON / XOFF or ^S / ^Q)
stty -ixon

Caps Lock is utterly useless. It is extremely seldom that I want to type a lot of stuff in upper-case, and when I do I'll just let my text editor upper-case it after I've written it.

More to the point, I use glorious vim, and the difference between pressing “ZZ” and “zz” is closing the editor without saving or scrolling my window so the cursor is in the middle.

Adapted from Handy Hack: Disable Caps Lock under GNOME.

Create/modify ~/.Xmodmap so it contains the following:

remove lock = Caps_Lock

That's it. Next time X is started, CapsLock will be disabled. If you want the change to take affect immediately (i.e. without logging out), use the following command:

xmodmap ~/.Xmodmap

http://www.stearns.org/doc/ssh-techniques-two.current.html

From: https://wiki.tcl-lang.org/page/Client+is+not+authorized+to+connect+to+Server

Copy xauth token from somewhere with access:

xauth extract - $DISPLAY

and import it to the place that's having trouble:

xauth merge -

For example, to allow a Docker container access to the X11 display:

xauth extract - $DISPLAY | base64

and copy the result to the clipboard, and then in the container shell:

base64 -d <<<'BASE64_GOES_HERE' xauth merge -