Basic Unix Commands

Unix commands are used to perform very specific tasks. There are many commands used to navigate/use unix file systems with command line interpreters. Lists of most of the commands available can be found in sections 3.2/5.1/5.2/5.3/5.4 of An Introduction to the Linux Command Shell For Beginners. These lists are quite extensive. The following table contains the most commonly used commands.

Command	Description	Example
pwd	Print working directory - Prints the file path to the current working directory.	pwd
ls / ls <path>	List - When used alone displays the contents of the current working directory. When used with <path> displays the contents of the directory found at <path>.	ls
cd / cd <path>	Change directory - When used alone switches to the root directory. When used with <path> changes from the current working directory to <path>.	cd desktop
touch <path>/<file>	Create File - Creates the <file> under <path>. This command will not create directories. This command only works on Unix/Linux/Mac.	touch file.txt
rm <path>/<file>	Remove File - Removes the <file> under <path>. This command will not remove directories.	rm file.txt
cat <path>	Concatenate - Displays the contents of the file at <path>.	cat log.txt
head <path>	Display beginning of file - Displays first 10 lines of the file located at <path>.	head log.txt
tail <path>	Display end of file - Displays last 10 lines of the file located at <path>.	tail log.txt
mkdir <path>	Make directory - Makes a new directory at <path>.	mkdir new
cp <path> <destPath>	Copy - Copies the file at <path> to <destPath>.	cp file.txt new/file.txt
mv <path> <destPath>	Move - Moves the file from <path> to <destPath>.	mv file.txt new/file.txt

Note: <file>/<path>/<destPath> must be valid files/paths from the current working directory.

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For the following examples use the following desktop as a reference for the questions:

Each of the following examples is a continuation from the previous example.

1. Use a Unix command to display the path to the desktop from the root directory.

alex@imac desktop % pwd
/Users/alex/desktop
alex@imac desktop % 

2. Use a Unix command to display all of the contents of the desktop.

alex@imac desktop % ls
blog		led		portfolio.pem	programs
alex@imac desktop % 

3. Use a Unix command to display all of the contents of the /programs directory.

alex@imac desktop % ls programs
main.cpp
alex@imac desktop % 

4. Use a Unix command to the home directory.

alex@imac desktop % cd
alex@imac ~ % 

5. Use a Unix command to display the current working directory.

alex@imac ~ % pwd
/Users/alex
alex@imac ~ % 

6. Use a Unix command to change to the programs directory contained in the desktop directory.

alex@imac ~ % cd desktop/programs
alex@imac programs % 

7. Use a Unix command to create a new file named new

alex@imac programs % ls
main.cpp
alex@imac programs % touch new
alex@imac programs % ls
main.cpp	new
alex@imac programs % 

This will cause a new file to display in the GUI:

8. Use a Unix command to make a new directory newDir with the file new in it.

alex@imac programs % touch newDir/new
touch: newDir/new: No such file or directory
alex@imac programs % mkdir newDir
alex@imac programs % ls
main.cpp	new		newDir
alex@imac programs % touch newDir/new
alex@imac programs % ls newDir
new
alex@imac programs % 

9. Use a Unix command to remove the new file from the current directory (/programs):

alex@imac programs % ls
main.cpp	new		newDir
alex@imac programs % rm new
alex@imac programs % ls
main.cpp	newDir
alex@imac programs % 

10. Use a Unix command to delete the newDir and all of it's contents:

alex@imac programs % ls
main.cpp	newDir
alex@imac programs % rm newDir
rm: newDir: is a directory

NOTE: DO NOT PERFORM THIS STEP ON ANY DIRECTORY UNLESS YOU WANT TO LOSE ALL OF THE DATA IN THE DIRECTORY PERMANENTLY. THIS DELETE IS UNRECOVERABLE

alex@imac programs % rm -rf newDir
alex@imac programs % ls
main.cpp
alex@imac programs % 

11. Use a Unix command to display all of the contents of main.cpp

alex@imac programs % cat main.cpp
#include <iostream>

using namespace std;

int main()
{
  cout << "Hello "
       << "Alex's "
       << "Blog"
       << endl;

  return 0;
}
alex@imac programs % 

12. Use a Unix command to display the first 10 lines of main.cpp.

alex@imac programs % head main.cpp
#include <iostream>

using namespace std;

int main()
{
  cout << "Hello "
       << "Alex's "
       << "Blog"
       << endl;
alex@imac programs % 

13. Use a Unix command to display the last 10 lines of main.cpp.

alex@imac programs % tail main.cpp

int main()
{
  cout << "Hello "
       << "Alex's "
       << "Blog"
       << endl;

  return 0;
}
alex@imac programs % 

14. Use a Unix command to move from the programs directory to it's parent directory.

alex@imac programs % cd ..
alex@imac desktop % ls
blog		led		portfolio.pem	programs
alex@imac desktop % 

15. Use a Unix command to copy the contents of /programs/main.cpp to the current directory and name the new file new.cpp.

alex@imac desktop % cp programs/main.cpp new.cpp
alex@imac desktop % ls
blog      led      portfolio.pem      programs    new.cpp
alex@imac desktop % 

16. Use a Unix command to move /programs/main.cpp to the current directory and keep the original name.

alex@imac desktop % mv programs/main.cpp main.cpp
alex@imac desktop % ls programs
alex@imac desktop % ls
blog     led     portfolio.pem     programs    new.cpp     main.cpp
alex@imac desktop %