Table of Contents
- Getting started
- Using ssh
- Logging in to eustis
- Ctrl-L to clear your screen
- Navigating the File System
- Running commands
- Where am i?
- What's here?
- Running commands with arguments
- Go to a new directory
- Go the parent directory
- Go to a subdirectory
- Making the command-line fast
- Tab-completion
- Editing commands
- Rerunning commands
- Viewing files
- cat command
- less command
- Downloading and untarring files
- Editing the file tree
- Removing non-empty directories?
- Review
- Orienting yourself
- Moving around
- Tab completion
- History
- Modifying the file tree
Getting started
Using ssh
See OS-specific guides in the syllabus
Logging in to eustis
ssh NID@eustis.eecs.ucf.edu
Then enter your password
You can create an ssh key and add it to eustis's .ssh/authorized_keys to login without a password.
# if you haven't already generated a key, run ssh-keygenssh-keygen# accept the default location (as long as you haven't already generated# now let's tell eustis about your public key (be sure to use .pub!)# linux/maccat ~/.ssh/id_rsa.pub | ssh NID@eustis.cecs.ucf.edu 'cat >> .ssh/authorized_keys'# windows (https://superuser.com/questions/1747549/alternative-to-ssh-copy-id-on-windows)type %USERPROFILE%\.ssh\id_rsa.pub | ssh NID@eustis.cecs.ucf.edu "cat >> .ssh/authorized_keys"# windows alternative (rsa_id.pub instad of id_rsa.pub)type %USERPROFILE%\.ssh\rsa_id.pub | ssh NID@eustis.cecs.ucf.edu "cat >> .ssh/authorized_keys"
Ctrl-L to clear your screen
Navigating the File System
Running commands
Type its name and hit <enter>
Where am i?
Print Working Directory: pwd
What's here?
LiSt the directory: ls
Running commands with arguments
Type its name, a space, then the argument.
Arguments are separate by spaces.
What if the argument has a space in it?
- escape the space with a backslash ~\ ~
- Use double-quotes (evaluates the contents, e.g., for bash variables and escape sequences)
- Use single-quotes (does not evaluate contents or escape sequences)
Go to a new directory
Change (working) directory: cd path
cd /usr/include
What kind of path is this, relative or absolute?
Use eustis's /usr/include as an example file hierarchy
These are where system-wide C header files are installed
Go the parent directory
cd ..
What is the .. directory?
Where are we now? How do we find out?
Get used to running pwd and ls to orient yourself
Go to a subdirectory
cd include
What kind of path is this, relative or absolute?
What if we had done cd ./include instead? What's the difference? Why do we have the . folder?
Making the command-line fast
At this point, you are typing a lot, and retyping some of the same paths over and over again.
Tab-completion
One of these most useful features for speed on the command-line
Works for files and directories, command-line arguments, and commands themselves.
You can even create completions for your own software.
Impatience
Don't spend time typing when you can use tab completion
Laziness
Don't try to remember yourself file names, let the shell do it
Example
- Be sure we are in
/usr/include Type the following, but don't hit <enter>
ls gnum
- Hit <tab>
The shell completes the file name for you!
ls gnumake.h
Multiple completions
Type the following, but don't hit <enter>
ls gnu
- Hit <tab>. Nothing seems to happen!
Hit <tab> again to see all completions.
/usr/include$ ls gnugnu/ gnumake.h gnu-versions.h /usr/include$ ls gnu
Add the hyphen and hit <tab> to complete.
ls gnu-
Completion happens only when there is a unique option. But hitting <tab> again will show all possibilities with the prefix written so far. Continue typing until you have a unique prefix, then hit <tab> again to complete the unique possibility.
Editing commands
| Keyboard | Description | Mnemonic |
|---|---|---|
| Ctrl-a | Beginning of command (home) | a is beginning of the alphabet |
| Ctrl-e | End of command | e for end |
| <backspace> | Delete a character behind you | it's the backspace key |
| Alt-<backspace> | Delete a whole word behind you | alt for alternative version |
| Alt-b | Go back a word | b for back, alt for alternative version |
| Alt-f | Go forward a word | f for forward, alt for alternative version |
https://www.gnu.org/software/bash/manual/bash.html#Commands-For-Moving
bash has emacs-like commands.
Additional commands
| Keyboard | Description | Mnemonic |
|---|---|---|
| Ctrl-d | Delete a character in front | d for delete |
| Ctrl-b | Move back | b for back |
| Ctrl-f | Go forward | f for forward |
| Alt-d | Delete a word in front | d for delete, alt for alternative version |
Kill (cut) and yank (paste)
| Keyboard | Description | Mnemonic |
|---|---|---|
| Ctrl-k | Kill (cut) until the end | k for kill |
| Alt-<backspace> | Kill (cut) a word to the back | alt for alternative version |
| Alt-d | Kill (cut) a word in front | d for delete, alt for alternative version |
| Ctrl-y | Yank (paste) | y for yank |
Rerunning commands
- History saves all commands your run
historywill print them all- Last command added to bottom of the list
Navigating the command history
| Keyboard | Mnemonic | Description |
|---|---|---|
| Ctrl-p or <up> | p for previous | Previous command |
| Ctrl-n or <down> | n for next | Next command |
Searching for a previous command
- Ctrl-r (r for reverse lookup)
- CAREFUL: hitting <enter> will immediately run
- Use ctrl-a or ctrl-e to start editing the command
- Ctrl-g to cancel search
Viewing files
| Command | Mnemonic | Description |
|---|---|---|
| cat | concatenate | write file(s) to terminal (stdout) |
| more | ask user to show more | write file out, pausing after each screenful |
| less | "less is more" | interactive command-line file viewer |
cat command
cat /usr/include/stdio.h
less command
less /usr/include/stdio.h
q to quit
Navigating less
- q to quit (try esc then q if not working, you might have hit other keys)
- pg-up, pg-down, up, down, left, right
- ctrl-v, alt-v, j, k, h, l
- / type pattern, then enter
- n for next
- N for previous
- type a number then G to go to line
- ctrl-g to show current command-line
The less command has vim-like commands.
Downloading and untarring files
| Command | Description |
|---|---|
| wget '<url>' | Download a file |
| tar -xvf file.tar | Unpack a tarball (x for eXpand, v for Verbose, f for Filename) |
cd ~/wget 'https://www.cs.ucf.edu/~gazzillo/teaching/cop3402fall24/files/hw3.tar'tar -xvf hw3.tarcd hw3
Editing the file tree
| Command | Description |
|---|---|
| touch | create file |
| rm | ReMove |
| mv | MoVe |
| cp | CoPy |
| mkdir | MaKe DIRectory |
| rmdir | ReMove (an empty) DIRectory |
Removing non-empty directories?
- Remove contents of the directory first, then use rmdir
- What's an algorithm to remove a whole directory tree?
You can ask rm to remove non-empty directories and their contents recursively, but it's a bit dangerous.
Review
Orienting yourself
pwd # to show your working directoryls # to list current directory contents
Moving around
cd /usr/include # to change working directorycd ../ # can use relative paths to, this puts you in /usrcd ~ # to go to home directorycd - # to go to last directorycd # also to go to the home directory
Tab completion
- Hit tab to auto-complete file and directory names
- Hit tab again to show all files with a matching prefix
- Use tab to quickly find paths
History
- Hit up (or Ctrl-p) to repeat the prior command
- Go up and down (or Ctrl-n) to step through the command history
- Hit enter on a command to rerun it
Modifying the file tree
touch filename # to create an empty regular filerm filename # to remove a (non-directory) filemv filename newname # to rename a filemkdir subdir # to make a new directorymv filename subdir/ # to move a filecp subdir/filename copiedname # to copy a filerm subdir/filename # to remove a filermdir subdir # to remove an empty directory
