Why GNU/Linux?

Software costs $0
Advanced Multitasking
Remote tasking (“real networking”)
Multiuser
Easy access to programming languages, databases, open-source projects
Software freedoms
1. Free to use for any purpose
2. Free to study and modify the source code
3. Free to share
4. Free to share modified versions
No dependence on vendors
Better performance
More up-to-date
Many more reasons…

Linux Basics - Command Line Basics

Basics

Command-Line Syntax for this Manual

Remember the UNIX/Linux command line is case sensitive!
All commands in this manual are printed in gray code boxes.
The hash (pound) sign “#” indicates end of a command and the start of a comment.
The notation <…> refers to variables and file names that need to be specified by the user. The symbols < and > need to be excluded.

Orientation

Viewing and changing the present working directory:

pwd               # "Print working directory"; show your current path

ls                # "List" contents of current directory
ls -l             # Similar to ls, but provides additional info on files and directories
ls -a             # List all files, including hidden files (.name) as well
ls -R             # Lists subdirectories recursively
ls -t             # Lists files in chronological order

cd <dir_name>     # "Change directory" to specified path
cd                # Brings you back to your home directory
cd ..             # Moves one directory up
cd ../../         # Moves two directories up (and so on)
cd -              # Go back to you were previously (before the last directory change)

The tilde symbol (~) gets interpreted as the path to your home directory when by itself or at the beginning of a word:

echo ~            # View the full (complete) path of your home
find ~            # List all your files (including everything in sub-directories)
ls ~              # List the top level files of your home directory
du -sch ~/*       # Calculate the "disk usage" of files in your home

Viewing file info, user, and host:

stat <file-name>  # Show last modification time stamps, permissions, and size of a file

whoami            # Shows your user name (same as "echo $USER")
hostname          # Shows on which machine you are (same as "echo $HOSTNAME")

Files and directories

mkdir <dir_name>   # Creates specified directory
rmdir <dir_name>   # Removes empty directory
rm <file_name>     # Removes file_name
rm -r <dir_name>   # Removes directory including its contents, but asks for confirmation
rm -rf <dir_name>  # Same as above, but turns confirmation off. Use with caution
cp <name> <path>   # Copy file/directory as specified in path (-r to include content in directories)
mv <name1> <name2> # Renames directories or files
mv <name> <path>   # Moves file/directory as specified in path

Copy and paste

The methods differ depending where you are.

In a command line environment:

Cut last word with keyboard only
Ctrl+w
Press multiple times to cut more than one word

Paste with keyboard only
Ctrl+y
In a non-command line desktop environment (e.g. Firefox):

Copy
Ctrl+c

Paste
Ctrl+v
Command line <-> desktop exchange:

Copy text out of the command line and into the desktop:
Shift+Ctrl+c or Apple+c

Paste text from the desktop into the command line:
Shift+Ctrl+v or Apple+v
On any Linux desktop!
- Copy with mouse only
  - Simply select the text with the mouse
- Paste with mouse only
  - Click the middle mouse button or both left/right buttons simultaneously

Handy shortcuts

At the command prompt:
- up(down)_key - scrolls through command history
- history # shows all commands you have used recently
Auto Completion:
- TAB - completes program_path/file_name
Taking control over the cursor (the pointer on the command line):

Ctrl+a    # Cursor to beginning of command line
Ctrl+e    # Cursor to end of command line
Ctrl+w    # Cut last word
Ctrl+k    # Cut to the end of the line
Ctrl+y    # Paste ("yank") content that was cut earlier (by Ctrl-w or Ctrl-k)

When specifying file names:
- ”.” (dot) - refers to the present working directory
- ”~” (tilde) or “~/” - refers to user’s home directory

Other Useful Unix Commands

df          # disk space
free -g     # memory info in Megabytes
uname -a    # shows tech info about machine
bc          # command-line calculator (to exit type 'quit')
wget ftp://ftp.ncbi.nih.... # file download from web
/sbin/ifconfig # give IP and other network info
ln -s <original_filename> <new_filename> # creates symbolic link to file or directory
du -sh      # displays disk space usage of current directory
du -sh *    # displays disk space usage of individual files/directories
du -s * | sort -nr # shows disk space used by different directories/files sorted by size

Unix Help

help <command>  # Show help for a Bash command
man <something> # Show the manual page for a program (press the 'q' key to exit) 
man wc          # Manual on program 'word count' wc
wc --help       # Short help on wc
soap -h         # For less standard programs 

Getting Started Linux