Essential Unix Commands and Functions
Commands
Function
Directory/Folder
A term refers to a folder used to organize different files and make locating them easier!
Bash
Bourne Again SHell
ls
lists the current working directory.
ls -F
tells ls to classify the output by adding a marker to file and directory names to indicate what they are:
- / – a trailing / indicates that this is a directory
- @ – indicates a link
- * – indicates an executable
-a
-a stands for ‘show all’ (including hidden files); it forces ls to show us file and directory names that begin with ., such as .. (which, if we’re in /Users/nelle, refers to the /Users directory).
ls [path]
prints a listing of a specific file or directory
ls -s
display the size of files and directories alongside the names
ls -S
sort the files and directories by size
cd [path]
changes the current working directory
PWD
prints the user’s current working directory
–
Most commands take options that begin with a single –
Unix-based (macOS, Linux)
/
Windows
\
/
on its own is the root directory of the whole file system
absolute path
specifies a location from the root of the file system.
relative path
specifies a location starting from the current location.
. or cd .
on its own means ‘the current directory
..
means ‘the directory above the current one’.
mkdir [path]
creates a new directory.
cp [old] [new]
copies a file.
mv [old] [new]
moves (renames) a file or directory
rm [path]
removes (deletes) a file.
*
* matches zero or more characters in a filename, so *.txt matches all files ending in .txt
?
? matches any single character in a filename, so ?.txt matches a.txt but not any.txt
Ctrl-X, Control-X, ^X
use of the Control key may be described in many ways
Delete
The shell does not have a trash bin: once something is deleted, it’s really gone
Most files’ names are something.extension
The extension isn’t required, and doesn’t guarantee anything, but is normally used to indicate the type of data in the file
wc
counts lines, words, and characters in its inputs.
cat
displays the contents of its inputs.
sort
sorts its inputs.
head
displays the first 10 lines of its input.
tail
displays the last 10 lines of its input.
command > [file]
redirects a command’s output to a file (overwriting any existing content)
command >> [file]
appends a command’s output to a file.
[first] | [second]
is a pipeline: the output of the first command is used as the input to the second.
|
is a “pipe”. The | takes the standard output of the command on the left, and pipes it as standard input to the command on the right. You can think of this as “command to command” redirection. Example: cat volcanoes.txt | wc
Ctrl+D
log out of current session, similar to exit
Ctrl+C
halts the current command
Ctrl+W
erases one word in the current line
Ctrl+U
erases the whole line
Ctrl+R
type to bring up a recent command
whoami
who you are logged in as
date
show the current date and time
cd ..
.. is a special directory name meaning “the directory containing this one”, or more succinctly, the parent of the current directory; moves one directory above it
cd –
It brings you back after using cd .. (takes to just previous opened directory).
~
The shell interprets a tilde (~) character at the start of a path to mean “the current user’s home directory”. For example, if Nelle’s home directory is /Users/nelle, then ~/data is equivalent to /Users/nelle/data
cd
shortcut to go back to the user’s home directory.
Desciption
