Unix Essentials

Unix Commands
Filename Completion
Command History
Stopping a Running Program
Editing on the Command Line
Basic Unix Commands

Unix Commands

Unix commands are typed at the command line after the prompt
They usually have the form
```
COMMAND  OPTION  ARGUMENT(S)
```
Where the options are usually preceded by "-" or "--"
Nothing happens until you hit the Enter key
Then the Unix shell, a command interpreter, tries to execute the command you have entered

Filename Completion

Two features of Unix that can save you considerable typing are:
- Filename completion
- Command history
Filename completion tries to finish a filename for you
After you hit the Tab key
It works as follows:
- Type part of the filename on the command line
- Hit the Tab key
- If there is only one filename that begins with those letters, Unix will supply the rest
- Sometimes Unix will supply a couple of characters and then beep
- This means there is more than one filename that matches the characters on the command line
- If you hit the Tab key a second time, Unix will show you the list
- If there is no filename that matches, Unix will just beep

Command History

Unix keeps a list of all the commands you type at the terminal
If you want to run the last command again, just hit the up arrow key, ↑
Unix will supply the last command you entered on the command line
Just hit Enter to run that command again
If you keep hitting the up arrow key, Unix will show the previous command
You can keep doing this as long as you like
To go in the other direction, hit the down arrow key, ↓

Stopping a Running Program

You have to wait for your last command to finish before you can run another command
But what if a program has a bug and keeps running?
In this case, you need to abort the program
In Unix you do this by holding down the Control key while hitting C (Ctrl-C)
This will kill the currently running program and allow you to run another command

Editing on the Command Line

The command line has some editing features that are similar to emacs commands
Ctrl A - Moves the text insertion point to the beginning of the current line
Ctrl E - Moves the text insertion point to the end of the current line
Ctrl U - Remove everything from the text insertion point to the beginning of the line
Ctrl K - Remove everything from the text insertion point to the end of the line
← - Moves the text insertion point one character to the left
→ - Moves the text insertion point one character to the right

Basic Unix Commands

pwd (print working directory)
- pwd gives you the location of your current directory
- It is used without an argument
```
pwd
```
ls (list)
- ls shows everything that is in a directory
```
ls  DIRECTORY
```
- If you run ls without an argument it lists your current directory
cd (change directory)
- cd moves you to another directory
```
	cd  DIRECTORY
```
- If you run cd without an argument it takes you to your home directory
- Use .. to go up one directory
```
cd  ..
```
mv (move)
- mv moves a file or directory from one place to another
```
mv FILE_OR_DIRECTORY_NAME  NEW_DIRECTORY
```
- You can also use mv to rename a file or directory
```
mv FILE_OR_DIRECTORY_NAME  NEW_FILE_OR_DIRECTORY_NAME
```
cp (copy)
- cp makes a new copy of a file
- To make a copy of the file in the same directory use
```
cp  ORIGINAL_FILENAME  NEW_FILENAME
```
- You can also make a copy in another directory
```
cp  ORIGINAL_FILENAME  DIRECTORY
```
- To make a copy of a directory, run cp with the -r (for recursive) option
cat (concatenate)
- cat prints the contents of a file
```
cat  FILENAME
```
rm remove
- rm deletes a file
- It does not work on directories
- There is no undelete in Unix
- To remove all files in the current directory, use
```
rm  *
```
mkdir (make dirrectory)
- mkdir creates a directory
```
mkdir  DIRECTORY_NAME
```
rmdir (remove directory )
- rmdir deletes a directory
- It will not work unless the directory is empty
```
rmdir  DIRECTORY_NAME
```
nano
- nano is a simple text editor
```
nano  FILENAME
```
- If the file does not exist, nano will create it
- You can find instruction on using nano here