A long time ago computers didn’t use a mouse and windows, the only way to work with them was using the keyboard and writing text. Now days that is not the case and most software you use will have a Graphical User Interface (GUI). This interface has menus that allow you to do things you want to do. But the old way of using a computer still exists and can be useful in many situations. The main advantage of the command line is that you can type thousands of words, many more choices then you could see on a menu. The main disadvantage is that you probably don’t know or want to know a thousand commands for your computer. However, once you know some commands it can be much faster to access them through the command line than a menu, and many commands can only be accessed through the command line.
Terminal
First you will need to run a program that emulates a terminal. There are many choices for this, the default on Mac OS X is called terminal. On Windows if you want to run Anaconda Python you should use the Anaconda Prompt. With Windows 10 you can also install a linux bash shell to run on your machine. Instructions.
The terminal is a screen that shows only text and you can only enter it at one place called the prompt. At the prompt you enter commands that are like words, though many commands aren’t actual words. Many commands can be modified with flags. Flags start with a – or –. Most commands have a help flag so
command --help
command -h
Unix Commands
There are thousands of commands in a standard unix distribution, you’ll only end up learning the few you find useful. Every command also has many options, usually given with a flag that start with a – or a –. Use man or the web to get a description of all the options. Below are some commands that I have found useful.
command > file |
redirect, >, sends what would be printed to the terminal instead to file, more options here |
cd dirname |
change directory, .. is up one directory and . is the current directory |
chmod filename |
changes the permissions of a file, u,g,o +/- r,w,x |
chown user filename |
changes the owner of a file to user |
cp filename1 filename2 |
copies filename1 to filename2 |
du dirname |
gives the amount of memory (disk usage) of the directory (or all files if no dirname is given) |
emacs -nw filename |
opens filename with emacs in the in the terminal (emacs must be installed) |
grep string filenames |
grep will search for the given string in a file |
head -N filename |
prints the first N lines of a file in the terminal |
less filename |
displays the text of a file in a the terminal |
ls |
list the contents of a directory, -a will list .files, -l will give more information |
man command |
prints the manual page of the command in the terminal |
mkdir dirname |
makes a directory names dirname |
more filename |
displays the text of a file in the terminal |
mv filename1 dirname |
moves a file to a different directory or renames it dirname if not a directory |
nohup command |
nohup before a command insures that the process won’t be killed if you kill the window |
pwd |
the present working directory is printed in the terminal |
rm filename |
removes a file permanently |
scp filename hostname:filename |
copies a file securely to or from a remote machine |
ssh user@hostname |
logs a user into a remote machine |
ssh-keygen -t rsa/code> |
generates a private/public key pair using rsa encryption |
ssh-copy-id -i hostname |
copies the key to a remote host (not installed on OSX use homebrew) |
tail -N filename |
prints the last N lines of a file to the terminal |
top |
prints the top jobs running on the cpu and information about them |
vim filename |
opens filename in the vi text editor in the terminal |
wc filename |
word count of filename, gives characters, words and lines |
which command |
gives full path of command |
