Linux Intro in DM500
====================

Material for the first hour
---------------------------

- ``pwd``: print stien til den nuværende mappe ("print working directory"). Hvor står vi henne i vores filsystem?
- ``ls``: list de elementer (mapper, filer) der er i den nuværende mappe.
- ``cd``: navigér rundt i filsystemet. Prøv at find hen til din mappe med Java-programmer fra DM550.

- ``cp``: lav en kopi af en fil eller mappe. Prøv at lav en kopi af DM550 mappen, som du kan rode rundt i med resten af kommandoerne.   
- ``touch``: lav en fil.
- ``rm``: fjern en fil (eller mappe).
- ``mkdir``: lav en ny mappe
- ``rmdir``: fjern en tom mappe.
- ``mv``: flyt/omdøb en fil eller mappe.

- ``man``: læs dokumentation for de forskellige kommandoer.
- ``grep``: sørg efter ting i filer. Prøv at køre ``grep -n public SomeClass.java`` med en af dine Java-filer i stedet for ``SomeClass.java``.
- ``find``: find filer eller mapper i dit filsystem. Prøv at køre ``find . -iname "*.java"`` i din DM550-mappe.
- ``wc``: tæl antal tegn, ord og linjer i filer.

Material from the second hour
-----------------------------

- `Figures <../../_static/teaching/linux/cmdGraphical.pdf>`__.

Additional material:

- `Unix Pipeline (Brian Kernighan) <https://www.youtube.com/watch?v=bKzonnwoR2I>`__, Computerphile on Youtube.
- `Standard streams <https://en.wikipedia.org/wiki/Standard_streams>`__, Wikipedia.
- `Pipeline (Unix) <https://en.wikipedia.org/wiki/Pipeline_(Unix)>`__, Wikipedia.


.. rst-class:: html-toggle section

Examples Commands
.................

How do I find out what a command does (e.g., ``ls``)?::

	man ls


How many lines of code in a file?::

	wc -l code.java

Where did I put my Java code?::

	find . -iname "*.java"

How many Java files do I have?::

	find . -iname "*.java" | wc -l

How many lines of code in each file?::

	find . -iname "*.java" | xargs wc -l

in sorted order?::

	find . -iname "*.java" | xargs wc -l | sort -n

and without the total count::

	find . -iname "*.java" | xargs wc -l | sort -n | head -n -1

or maybe just the total::

	find . -iname "*.java" | xargs wc -l | sort -n | tail -n 1


Search for a string in all files::

	grep -Rn "^class "

How many matches?::

	grep -Rn "^class " | wc -l


Download a webpage, and just print the raw HTML to the terminal::

	wget -O - http://dr.dk

Find all lines in the page with links::

	wget -O - http://dr.dk | grep http

Extract just the link from the line::

	wget -O - http://dr.dk | grep http | sed "s/^.*http/http/" | sed "s/\".*//" | sed "s/\?.*//"

Sort the links, and filter out duplicates::

	wget -O - http://dr.dk | grep http | sed "s/^.*http/http/" | sed "s/\".*//" | sed "s/\?.*//" | sort | uniq

Filter out those linking to the same domain::

	wget -O - http://dr.dk | grep http | sed "s/^.*http/http/" | sed "s/\".*//" | sed "s/\?.*//" | sort | uniq | grep -v "www.dr.dk"


Someone in my group changed something in a file, but what?::

	diff -u original.java changed.java