[manjaro] install packages from AUR

November 23, 2014 Leave a comment

See here: https://forum.manjaro.org/index.php?topic=7299.0.

In short:

# install yaourt
sudo pacman -S yaourt

# install with yaourt from AUR
yaourt -S <package>

# update the packages installed from AUR
yaourt -Syua
Categories: manjaro Tags: , ,

shopt: change additional shell optional behavior

November 22, 2014 1 comment

There is a command called shopt that allows you to change additional shell optional behavior.

I use both Ubuntu and Manjaro and I noticed that sometimes bash behaved differently on Manjaro. For instance, I had a folder called “Test_me”. Once accidentally I wrote “cd test_me” and Manjaro entered the folder “Test_me” (notice the capital ‘T’) without any problem. Under Ubuntu it was impossible :)

As it turned out, the different behaviour is due to different shopt settings. In the example above, “cdspell” was on in Manjaro, while in Ubuntu it was off by default.

Since I use both systems and I want bash to behave similarly, I added these lines to the end of my ~/.bashrc:

# shopt settings (normalize Ubuntu and Manjaro)
shopt -s cdspell
shopt -s dotglob
shopt -s hostcomplete
shopt -s nocaseglob
shopt -u sourcepath

I switched “sourcepath” off. Read this post if you want to know why.

Categories: bash, manjaro, ubuntu Tags: ,

the command “source” doesn’t exactly work the way you thought

November 22, 2014 1 comment

We know that “source” is a bash shell built-in command that executes the content of the file passed as argument in the current shell. It has a synonym: ‘.‘ (dot).

The classical use case is “source .bashrc” in your HOME directory. You do it when you modify your ~/.bashrc file and you want to activate the changes in the current terminal.

TIL something new. I had a discussion about it at reddit and the user geirha gave such a clear answer that I would quote him:

“The . (source is an alternative name for . in bash) command behaves more or less the same as when executing a command.

In POSIX sh, the following two will search for a file named foo in PATH (only).

    foo
    . foo

while the following two will specifically run and source, respectively, the file named foo in the current directory (only)

    ./foo
    . ./foo

Bash differs slightly (when not running in posix mode) in that when you give . or source an argument without any slash (/) characters (e.g. source foo), it searches through the PATH variable, like POSIX sh, but then also checks the current directory, if it was not found in PATH.” (end of quote)

Problem
Because of this I ran into a strange problem. I had a file called “.venv” that I wanted to source (source .venv) but I got some error. If I renamed the file, it worked well. But I wanted to call it “.venv”. What’s wrong?

Explanation
As explained above, it turned out that “source” started to look for “.venv” in the PATH first. Somehow it found a different file with the very same name and that caused the problem. When I renamed the file to “not_hidden” or “.jabba”, it worked.

Solution #1
The trivial way is to use “./” by telling source to take the argument from the current directory:

source ./.venv

However, in my entire life I thought that “source .bashrc” takes the file .bashrc from the current directory. It should, in my opinion :)

Solution #2
If you also think that “source” shouldn’t do anything with the PATH variable, there is a cure. This feature can be switched off. The command “shopt” is a builtin that allows you to change additional shell optional behavior.

The guilty option is this one:

sourcepath

    If set, the source builtin uses the value of PATH to find 
    the directory containing the file supplied as an argument. 
    This option is enabled by default.

Simply run “shopt” to see if “sourcepath” is on for you. You can switch it off easily:

shopt -u sourcepath

To make it permanent, add this line to the end of your ~/.bashrc.

After all this ado, I could finally write this:

. .venv

And this is the beauty of Linux. You learn something new every day :)

Links

Categories: bash Tags: , , , ,

command-line currency converter

November 19, 2014 Leave a comment

Qalculate! is a multi-purpose desktop calculator for GNU/Linux (now ported to Mac). It is small and simple to use but with much power and versatility underneath. Features include customizable functions, units, arbitrary precision, plotting, and a user-friendly interface (KDE or GTK+).” (source)

The software has a command-line interface too that you can start with the command “qalc“. You can do all kinds of fancy math calculations with it, but this time I’m interested in currency conversions. Qalc supports it too:

$ qalc
You need the download exchange rates to be able to convert between different currencies.
You can later get current exchange rates with the "exchange rates" command.
Do you want to fetch exchange rates now from the Internet (default yes)? yes
> 50000 USD to HUF

  50000 * dollar = approx. HUF 12157958

>  USD to HUF

  dollar = approx. HUF 243.15915

>

Related

colorize man pages

November 19, 2014 1 comment

Before
before

After
after

But how?

sudo apt-get install most

Then add this line to your ~/.bashrc:

export PAGER=most

Open a new terminal and try it.

Explanation
This tip is from here. As the user cannedprimates states, “you can solve this issue by using a different pager, for example most. man will actually use the program specified in the PAGER environment variable.”

Categories: bash Tags: , , , ,

autocompile LaTeX project when a file changes

November 19, 2014 Leave a comment

Problem
When I work with LaTeX, I always create a script called “compile.sh” that compiles the project and produces a PDF. For viewing the PDF file I use okular since it refreshes automatically if the PDF changes. However, if I change the LaTeX source, I need to call the “compile.sh” script manually. Could it be automated? That is, when I save the LaTeX source, the project should compile automatically, so I should only switch between my text editor and the PDF viewer.

Solution
I found a complete solution for the problem: autocompile.py. It’s a demo script that is part of the pyinotify project.

Usage:

./autocompile.py . .tex,.bib ./compile.sh

I put autocompile.py in the root folder of the LaTeX project, next to the compile.sh script. The command above means the following: “monitor the current directory recursively. When a .tex or .bib file changes, call the compile.sh script.”

Related

Categories: python Tags: , , , ,

Learn a language in a few minutes

November 16, 2014 Leave a comment

Short summaries of different programming languages: http://learnxinyminutes.com/ .

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