Intro to DCU Linux (command-line)

There may be a choice of command-lines. Search for "terminal" or similar.

Terminal

Terminal
- Default shell is bash. Other shells are installed.
- Increase font is Ctrl + which on your keyboard may translate to Ctrl Shift +
- Decrease font is Ctrl -
- In GNOME Terminal, if a URL appears in the text on the command-line, you can right-click on it to open it in browser.
Command-line keys:
- Ctrl-C - interrupt program
- Ctrl-A - Home
- Ctrl-E - End
- Command line shortcuts
- clear - clear screen
ls
- ls
- ls -l
- echo * (all normal, non-hidden files and dirs)
- ls -l * (if dir, will display contents)
- ls -ld * (if dir, display name not contents)
hidden files
- ls -a
- ls -al
- echo .* (all hidden files)
- echo .* * (all files)
- ls -l .* (don't need -a if going to actually name the hidden files)
- ls -ld .*
environment variables
- set
- set > file.txt
- env
- env | sort
- echo HOME - the string "HOME"
- echo $HOME - the global (environment) variable HOME
- PATH = list of dirs searched for command when you type a command, separated by colons (:)
- SHELL = shell we are using (default here is bash)
Shared, multi-user, file system:
- HOME = something like:
```
  /users/yourgroup/yourusername 
```
- My test account is here:
  /users/tutors/mhumphrysdculab
current and parent dirs
- . (current dir)
- .. (parent dir)
- Example: Run a program that is in the current dir but not in the PATH:
```
 ./prog 
```
cd
- go home: cd
- go up to parent dir: cd ..
- go back to last dir: cd -

Command-line text editors

nano
nano shortcuts:
- Ctrl-W - Find
- Ctrl-K - Delete line
- Ctrl-A - Home
- Ctrl-E - End
- Ctrl-Y - PgUp
- Ctrl-V - PgDn
- Alt \ - Start of file
- Alt / - End of file
- Alt Y - Syntax colours off
- Ctrl-O - Save
- Ctrl-X - Exit
vi

 
vim commands: 
Esc - menu  
:w - save  
:q - quit

history

up/down arrows
history
This is long to type, so we often set up an alias like: h
!n - repeat command n
!string - repeat last command that began with string
!c - repeat last command that began with character c
!! - last command
Clear history: history -c

Disk quota

To see your disk quota, type:

 
 quota -s

quota manual page
Last we checked: You have 2 G disk quota.

If you get "Disk quota exceeded"

You need to delete some files.
To see which dirs are taking up room:
```
du | sort -n 
```
There may be a DCU script to help you delete unneeded files. Try:
```
 purge-junk-files 
```

Misc

Installing and updating applications on Linux is easy (if you have administrator rights):
- APT package management tool ("apt-get" command)
- Will need administrator rights to modify system directories. (e.g. Install Linux on your laptop and try it.)
- winget Package Manager for Windows 10 up. Can use "winget" on the Windows command line.
- Package managers on different OSes.
- List of package managers

Works of Shakespeare

For testing manipulation of data with Linux commands, it helps if we have some data to manipulate. So I have installed the works of Shakespeare to use for testing.

Core information you need

The works of Shakespeare are on the shared file system here:
```
  /users/tutors/mhumphrysdculab/share/shakespeare 
```
You can "cd" to this directory.
If you cannot see that directory, there is something wrong with your lab machine. This has happened before, and the cause is mysterious. Solution: Switch to another lab machine.

More on the Shakespeare files

Source:
- I downloaded this copy of the works of Shakespeare from the free eBooks site at the University of Adelaide.
- This has now closed. There are old copies in the Internet Archive at:
  - Shakespeare page
  - ZIP file
Web pages not on the web:
- These are web pages, but are not on the web. You cannot view them through http.
How to view these web pages:
- You can still view these pages through a web browser, using this URL:
```
 file:///users/tutors/mhumphrysdculab/share/shakespeare/home.html 
```
- Or get to them using the file manager, and double click on them.
- I cannot link from here (a http page) to the above URL. You have to paste the URL into your address bar.
- Browsers do not allow links from http: to file: for security reasons.
- Once you are in file: mode, you can follow the links from file: to file:
How do I share these files with you?
- I am sharing these through the shared file system. Permissions need to be something like:
```
 drwx--x--x  /users/tutors/mhumphrysdculab  
 drwxr-xr-x  /users/tutors/mhumphrysdculab/share 
```

These Shakespeare files use relative HTML links, not absolute HTML links, so can download to any location and the links still work ok.