If you run into any problems, check out the Troubleshooting section.
# The One Command That Everyone Should Know... is 'man'.
# Every command has it's own manual page.
# Want to know a command's purpose and/or usage? Read it's man page!
# Usage: man [topic]
ryan@delta ~ $ man ls
# Usage: man -k <search_term>
ryan@delta ~ $ man -k zip
bzip2 (1) - a block-sorting file compressor, v1.0.6
gzip (1) - compress or expand files
zip (1) - package and compress (archive) files
A command synopsis tells you how to use a command. It looks like this:
# command <mandatory> [optional]The synopsis for the echo command (straight from the man page):
# echo [SHORT-OPTION]... [STRING]...The '...' means that you can repeat that part.
Now we can see that the echo command takes
multiple & optional short options and also multiple & optional
strings.
## Navigation ##
ls [dir] # List directory contents
ls -a # List all contents, i.e. hidden files
ls -l # Long listing
ls -1 # List every item on a new line
ls -lh # Long listing, human readable
ls -lh *.jpg # List all .jpg files
cd [dir] # Change into directory
cd .. # Go up a directory
cd ../.. # Go up two directories
cd / # Go to root directory
pwd # Print working directory
du -sh # Show directory's disk usage## File Manipulation ##
touch <file> # Create file
mkdir <dirname> # Make a directory
cat <file> # Output file contents
wc -l <file> # Count lines in file
wc -w <file> # Count words in file
wc -c <file> # Count characters in file
grep <pattern> <file> # Search file for pattern
head [-n lines] <file> # Get n lines from the top of the file
tail [-n lines] <file> # Get n lines from the bottom of the file
rm <file> # Remove file
rm -r <folder> # Remove recursively
rm -rv <folder> # Remove recursively and verbosely
rm -f <file> # Remove forcefully
cp <src> <dest> # Copy a file
mv <src> <dest> # Move a file
ln <file> <link> # Create a hardlink
ln -s <file> <link> # Create a symlink## Information & Administration ##
date # Show date and time
w # Show who is logged in and what they are doing
top # Dynamic process list
kill <pid> # Kill a process based on PID (Process ID)
kill -9 <pid> # Force kill PID
killall <process_name> # Kill a process based on name## Other ##
echo <string> # Output a string
sleep <seconds> # Pause for n seconds## Terminal Shortcuts ##
Ctrl+C # Kill current process
Ctrl+L # Clear terminal
Ctrl+A # Move cursor to beginning of prompt
Ctrl+E # Move cursor to end of prompt
Ctrl+Shift+C # Copy terminal selection to clipboard
Ctrl+Shift+V # Paste clipboard into terminal
Shift + Page Up/Down # Scroll up/down the terminal
## Braces! ##
echo {1,2,3} # Expands to "1 2 3"
echo {1..5} # Expands to "1 2 3 4 5"
echo {01..05} # Expands to "01 02 03 04 05"
echo {a..e} # Expands to "a b c d e"
echo {word1,word2,word3} # Expands to "word1 word2 word3"
mkdir {A..Z} # Creates 26 directories named A thru Z
touch File_{A..C} # Creates files: File_A, File_B, and File_C
touch main.{c,h} # Creates files: main.c and main.h
* represents anything. Hello*.txt would satisfy 'HelloWorld.txt', 'Hellooo.txt', etc.
? represents a single character. R?an would satisfy 'Ryan', 'Raan', 'Rban', etc.
## Wildcards! ##
ls *.jpg # List all files with the .jpg extension
rm *.jpg # Remove all .jpg files
rm ??.txt # Remove all two character .txt files
rm * # REMOVE EVERYTHING!!!## Semi-colon Operator ##
# means 'do that after this'
ryan@delta ~ $ echo hello; echo world
hello
world
## && Operator ##
# means 'only if successful, do that after this'
ryan@delta ~ $ echo hello && echo world
hello
world
ryan@delta ~ $ Fake_Command && echo world
bash: Fake_Command: command not found
## || Operator ##
# means 'only if failure, do that after this'
ryan@delta ~ $ Fake_Command || echo "Failure!"
bash: Fake_Command: command not found
Failure!
## Mixing semi-colon, &&, and || ##
ryan@delta ~ $ touch MyFile
ryan@delta ~ $ echo "Removing..."; rm MyFile && echo "Yay!" || echo "Boo!"; echo "Done."
Removing...
Yay!
Done.
ryan@delta ~ $ echo "Removing..."; rm MyFile && echo "Yay!" || echo "Boo!"; echo "Done."
Removing...
rm: cannot remove ‘MyFile’: No such file or directory
Boo!
Done.
## BASH Job Control ##
<command> & # Run command in the background
<command> &>/dev/null # Suppress command's output
<command> &>/dev/null & # Suppress command's output and run in background
Ctrl-Z # Stop current process
fg # Put stopped process in foreground
bg # Put stopped process in background
jobs # List current running jobs## File Permissions ##
chmod +x <file> # Make file executable
chmod -x <file> # Make file not executable#############################
## Piping ##
#############################
# Takes the output of one command and uses it as the input to another.
#
# Here we'll get the number of files in directory by counting lines
# of 'ls' by using the command 'wc -l'.
ryan@delta ~ $ ls
01 02 03 04 05 06 07 08 09 10
ryan@delta ~ $ ls -1 | wc -l
10#############################
## Redirection to a File ##
#############################
# Use the '>' operator to save the output of a command to a file.
ryan@delta ~ $ ls
ryan@delta ~ $ echo "Hello world!" > file
ryan@delta ~ $ ls
file
ryan@delta ~ $ cat file
Hello world!
# Use the '>>' operator to append to the file instead of overwriting.
ryan@delta ~/example $ echo "I am on line two!" >> file
ryan@delta ~/example $ cat file
Hello world!
I am on line two!This is because of how BASH handles strings. BASH strings must be
single-quoted, double-quoted, or space-escaped.
An Example:
# Let's create a file called: Hello World.txt
ryan@delta ~ $ touch Hello World.txt
# Uh oh, BASH interpreted our filename as two separate strings
ryan@delta ~ $ ls
-rw-r--r-- 1 ryan users 0 Sep 26 19:03 Hello
-rw-r--r-- 1 ryan users 0 Sep 26 19:03 World.txt
# Let's try it with single quotes
ryan@delta ~ $ touch 'Hello World.txt'
ryan@delta ~ $ ls -l
-rw-r--r-- 1 ryan users 0 Sep 26 19:03 Hello World.txt
# Let's try it with double quotes
ryan@delta ~ $ touch "Hello World.txt"
ryan@delta ~ $ ls -l
-rw-r--r-- 1 ryan users 0 Sep 26 19:03 Hello World.txt
# Let's try it with space-escaping (a backslash before every space)
ryan@delta ~ $ touch Hello\ World.txt
ryan@delta ~ $ ls -l
-rw-r--r-- 1 ryan users 0 Sep 26 19:03 Hello World.txt
# Oh boy! They all work!
Certain symbols have specific meanings in BASH. Such as the semi-colon, &&, ||, or exclamation mark. Single-quotes tell BASH to interpret the string literally.
# Exclamation mark in double quotes. Boo, it fails.
ryan@delta ~ $ echo "I! AM! A!WEIRD!STRING!"
bash: !WEIRD!STRING!: event not found
# Exclamation mark in single quotes. Yay, it works!
ryan@delta ~ $ echo 'I! AM! A!WEIRD!STRING'
I! AM! A!WEIRD!STRING