Commands
Core commands
pwd - show the current (or “working”) directory. Stands for “print working directory”
ls - show the files and folders in the working directory. I think of it as standing for “list stuff,” but it’s probably just short for “list.”
ls -1- show the files and folders in a nice vertical column.
cd - move to a directory, i.e. cd Desktop will move to the “Desktop” folder. Some special cases:
cd ..- go to the directory abovecd ~go to your “home” directory, i.e. /Users/cd(by itself) also goes to the home directorycd -go to the last directory you were in before the currentcd ../..travel two directories upcd Documents/thesis-draftsmove two directories, from the home folder to “thesis-drafts,” skipping “Documents”
touch <filename> - Create an empty text file named <filename> in your current directory.
atom <filename> - Open file in atom (and create it, if it does not already exist).
mkdir <folder name> - Create a directory named <folder name> in the current working directory.
echo <some text> - Print out any text you give it. Often used with a redirect to add text to a file.
cat <filename> - Print the contents of a file to the screen, in this case the contents of <filename>
> - Redirects printed output to a text file. For example echo "this is some text" > hello.txt would put “this is some text” in a file called hello.txt
>> - Redirect and append. If there’s already a file with text in it, this command will add that text to the file without destroying and recreating it.
| - Pipe symbol. Takes output from one command and uses it as input for another command.
less <filename> - Print out the contents of a file in a paginated form. Use <Control-v> and <Alt-v> (or <Command-v and <Option-v>) to move up and down. Press q to quit.
head <filename> - Print the first section of a file (first 10 lines or other specified quantity)
tail <filename> - Print the last section of a file (last 10 lines or other specified quantity)
wc -l - Takes input and returns the number of lines in that input, as in cat <filename> | wc -l
sort - Arrange lines in a file in numeric and alphabetical order.
uniq - Remove duplicate lines from input, as in cat <filename> | uniq. To show the duplicate files, use uniq -d. Often most useful after using sort, since it only removed duplicates that are next to one another.
mv - Move or rename a file. For example, mv file1 file2 will rename file to file2. You can also specify another destination, so that mv file1 ~ will move file1 to the home folder without renaming it.
rm <filename> - Permanently remove a file from your computer.
clear - Clears our terminal window of the command history (you can also type Control + l).
grep -i <text> - Searches text and prints any line that matches a specified pattern (here “text”). “Grep” stands for “global regular expressions.”
rev - Reverses the text you give it, i.e. echo "Hello there" | rev
Other useful commands
<tab> - The <tab> key on your keyboard will complete names of commands and files. Start typing a filename and hit tab twice to see all possible acceptable completions. If there is only one possibility, the rest of the name will be filled in for you.
<up> - The <up> key will fill in the last command you ran. Hit it multiple times to cycle through the last commands you’ve entered.
man <command name> - The man or manual command will provide information on any UNIX command. Try man ls, man grep, or man man.
exit - Exit the terminal session. You can also use <Control-d>
sudo - Run before a command to run it as an administrator. You will need to enter your password, and note that no asterisks or special characters will appear as you type.
su - Become the root user of the system. Your $ prompt will change to a # prompt.
!! - Run the last command. To run the last command you entered with administrative privileges, use sudo !!
* - refer to all files and folders in a directory, i.e., cat *.txt
clear or <Control-l> - Clear the terminal window.
which - Show where a command is stored on your system, i.e. which python
history - See the previous commands you’ve entered in the terminal. Useful in conjunction with grep
cp - Copy a file. cp file1 file2 will make a copy of file1 named file2. Can be used with the -r flag to copy whole folders.
rm - This command can be dangerous, so use it carefully. Removes a file or files. If used with the wrong flags or in the wrong place, you can delete a lot of important files, so be careful with this one.
rmdir - Remove an empty directory.
. and .. - . Refers to the folder you’re in, while .. refers to the folder above.
.hello.txt - Any file with a . in front of its name is a hidden file. You won’t see it in ls or in the GUI. To reveal hidden files, use ls -A
ping - Use ping google.com to see if your internet is working.
df -hl - Tells you how much hard drive space you have left.
top - Monitor which processes are using up your memory
kill and killall - Kill a particular process or kill a category of processes by name. Try killall chrome or killall firefox
sudo shutdown -r - Reboot the computer. shutdown -h turns off the computer.
time - Use before a command to find out how long that command takes to run.
uptime - Tells how long your computer has been on.
Not particularly useful commands
cal - Show a calendar.
telnet towel.blinkenlights.nl - Watch Star Wars in the terminal. Because.
say "Hello there" - Have your computer talk to you. (Use espeak on Linux.)
Find so much more on the command line:
Bash manual - the no nonsense text descriptions of bash commands.
explain shell - a site that explains commands you paste into the form. This site is fantastic for breaking down commands you find in the wild on the internet.
Easy shell guide - a friendly, styled (pastel!) list of common commands you might want to try out.