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Quick guide

Why use Linux?

Well, how does it differ from Windows? Let's list up some of the greatest points:

  • Full access. Linux is open source, you can read how it all works.
  • Great terminal in Linux, not so great in windows.
  • Package manager in Linux.
  • Flexibility. So which Desktop Environment do you want? What package manager? etc.

Basic commands

Change directory

  cd {directory}

List directory

  ls [-lha]

Create a new file

  touch {file}

Copy file or directory

  cp [-R] {source} {destination}

Move file or diretory (also used for renaming)

  mv {source} {destination}

Run a the program program (if it's executable)

  ./program

Print working directory

  pwd

The list goes on. See the links fore more.

Wildcards

What if we wanted to list all .pdf files? Or all .tex and .fsx files?

List all pdf files

First change directory into wildcard

  cd wildcard

List files using the asteriks regular expression

  ls *.pdf

This regular expression will expand to any files ending in .pdf. In this case, it's the files 'whatever.pdf' and 'foobar.pdf'

Listing all .tex and .fsx

  ls *.{tex|fsx}

Case: Find the needle in a haystack

  grep -n -e needle files/*.txt

Piping

Show good example of piping

First, type this into the terminal:

  wc -l

Then type in random things, and terminate with ^d (Ctrl + d). The terminal will output number of lines

How many files are there in the current directory? The command wc -l will list the number of lines of STDIN. If we pipe the output from ls -l into STDIN for wc -l, it will effectively count the number of files in the directory. Voila!

  ls -l | wc -l

This can be used for much elaborate usecases. Grep multiple files for specific lines, find duplicates, make them all lowercase and save to a file. All of these operations can be done by seperate command line tools by piping the output of one command as the stdin of the next command. This generate a so called "pipe" between several commands.

Redirection

Redirecting STDIN

Redirect STDIN to come from a file, instead of the keyboard.

First, run the program simple in the cprogam directory. This can be done by typing this into the terminal

  cd cprogram

Make sure the cprogram is executable, by typing in the following

  chmod +x simple

Now, run the program by typing

  ./simple

Enter the requested information. Manually entering stuff is cumbersome. Let's automate that!

simple reads from STDIN using the scanf function from stdio. STDIN is by default the keyboard, but using redirection, we can change that. To ru a program prog with a file input as STDIN, type the following into the terminal:

  ./prog < input

In our case, type in the following:

  ./simple < input.txt

Show when to use redirection. For example, their fsx script might be reading from stdin, then redirection could be a good thing to use. STDIN should come from this file.

Redirecting STDOUT

Just like the STDIN can be redirected, the STDOUT can be redirected as well. Say we want

Links