Beginner’s Guide to Shell Commands

Maybe you just began to use Linux, or maybe you need to run programs in Terminal/Shell, in both cases, you need a command reference or cheat sheet. Here’s what you’re looking for, a list of some basic commands with examples.

1. Work on Directories (or Folders in Windows)

ls : list

ls : to list all the directories/files in the current directory(folder).

pwd : present working directory

pwd: to show the current file path.

cd : change directory

cd folder_name: to change directory to the directory(folder).

For example, cd folder1 changes the directory to the subfolder “folder1” in the current folder.

Three special signs for directory:

• . : current directory

• .. : parent directory, thus cd .. means changing to the parent directory.

• ~ : home directory, thus cd ~ means changing to the home directory. We can also type cd for the same result.

mkdir : make a directory

mkdir folder_name : to make a new directory (folder).

rm -r : remove

rm -r folder_name : to remove the whole directory (folder) ( “-r” means recursively).

Warning: In UNIX, when you rm a file or directory, it's gone. There is no Recycle bin or Trash for you to "undo" rm, so please think twice before you use it.

2. Work on Files

echo : similar to “print”

echo content : to print the content on the screen.

echo content>>filename.filetype: to write to the file.

cat : display

cat filename.filetype : to display the content of the file.

touch : create a file

touch filename.filetype: to create a new empty file.

The following example uses these three commands. First we use echo to print “hello” on the screen :

>echo "hello!"
hello!

Then we create a new directory named “example”, and use touch to create a new txt file named “ex01” in it.

>mkdir example
>cd example
/example> touch ex01.txt
/example> ls
ex01.txt

When we type cat ex01.txt, the output is nothing, because “ex01.txt” is an empty file.

/example> cat ex01.txt

We can use echo command to write something into “ex01.txt” :

/example> echo "hello">>ex01.txt

Now using cat command, we’ll see the content of “ex01.txt”:

/example> cat ex01.txt
hello

We can also write many times, the content will be added to the file :

/example> echo "Let us learn Python.">>ex01.txt
/example> cat ex01.txt
hello
Let us learn Python.

mv : move

mv source_path dest_path ：to move the file/directory from the source_path to the dest_path.

There are two ways of using mv:

1.mv source_file/directory dest_directory : to move the source file/directory to the dest_directory

2.mv source_file dest_file : to rename the source_file, now the file name is dest_file. If dest_file has already existed, it will be overwritten as the content of the source file.

Let’s see an example. Here we still use the “example” folder in the previous example, with “ex01.txt” inside it.

/example> ls
ex01.txt

First we create a new folder named “sub_example” as the dest_directory.

/example> mkdir sub_example
/example> ls
ex01.txt  sub_example/

The folder “sub_example” is empty now:

/example> ls sub_example

(1) use mv source_file/directory dest_directory to move a file :

/example> mv ex01.txt sub_example

Now the file “ex01.txt” is in the subfolder “sub_example”, not in the folder “example”:

/example> ls
sub_example/
/example> ls sub_example
ex01.txt

(2) use mv source_file dest_file to rename a file :

/example> cd sub_example
.../sub_example> mv ex01.txt ex02.txt

Here the file name is changed from “ex01” to “ex02”.

.../sub_example> ls
ex02.txt
.../sub_example> cat ex02.txt
hello
Let us learn Python.

You may wonder: what will happen if the dest_file has already existed?

We create a file “ex03.txt” with the content “another txt file”.

.../sub_example> touch ex03.txt
.../sub_example> echo "another txt file">>ex03.txt
.../sub_example> cat ex03.txt
another txt file

After typing mv ex02.txt ex03.txt, there will be a prompt to check if you really want to overwrite dest_file “ex03.txt”.

.../sub_example> mv ex02.txt ex03.txt
mv: overwrite 'ex03.txt'? y

If you type “y”, “ex03.txt” will be overwritten as the content of “ex02.txt”.

.../sub_example> ls
ex03.txt
.../sub_example> cat ex03.txt
hello
Let us learn Python.

cp : copy

cp file/directory dest_directory: to copy the file/directory to the dest_directory.

For mv/ cp command, if the dest_directory is the current directory, we can write . instead.

rm : remove

rm file_name: to remove a single file. Here only a file is removed, so -r is not needed.

unzip

unzip file_name.zip : to unzip the .zip file.

3. Others

man command_name: to display manual pages for the command.

Reference

Lab 0: Getting Started | CS 61A Fall 2020

UNIX tutorial | CS 61A Fall 2020

touch command in Linux with Examples - GeeksforGeeks