Here is a review of commands and concepts that we have covered so far.


We have covered the following commands so far:

treetree -dfL 1List directories, full path, one level
cdcd ~change to home directory
cd /change to root directory
cd binchange to bin directory from current directory
pwdpwdprint working / current directory
lsls ~list home directory contents
ls -allist long format and hidden files in current directory
ls -dllist long format the current directory
manman lsopen manual page for the ls command
man manopen manual page for the man command
cpcp * bin/copy all files in current directory to bin subdir
mvmv oldname newnamerename file oldname to newname
mv oldir bin/newdirmove oldman to bin subdir and rename to newdir
rmrm oldfiledelete file named oldfile
rm -r olddirdelete directory olddir and its contents
touchtouch newfilecreate a file called newfile
touch oldfilemodify timestamp of file called oldfile
mkdirmkdir newdircreate a new directory called newdir
rmdirrmdir newdirdelete directory called newdir if empty
echoecho "hello"print "hello" to screen
catcat data.csvprint contents of file called data.csv to screen
cat data1.csv data2.csvconcatenate data1.csv and data2.csv to screen
lessless fileview contents of file called file
sudosudo commandrun command as superuser
chownsudo chown root:root filechange owner and group to root of file file
chmodchmod 640 filechange permissions of file to -rw-r-----
chmod 775 somedirchange permissions of of somedir to drwxrwxr-x
groupsgroups userprint the groups the user is in
wcwc -l fileprint number of lines of file
wc -w fileprint number of words of file
headhead fileprint top ten lines of file
head -n3 fileprint top three lines of file
tailtail fileprint bottom ten lines of file
tail -n3 fileprint bottom three lines of file
cutcut -d"," -f2 data.csvprint second column of file data.csv
sortsort -n filesort file by numerical order
sort -rn filesort file by reverse numerical order
sort -df filesort file by dictionary order and ignore case
uniquniq filereport or omit repeated lines in sorted file
uniq -c filereport count of duplicate lines in sorted file

In addition to the above commands, we also have pipelines using the |. Pipelines send the standard output of one command to a second command (or more). The following command sorts the contents of a file and then sends the output to the uniq command to remove duplicates:

sort file | uniq

Redirection uses the > or the >> to redirect output of a command to a file. A single > will overwrite the contents of a file. A double >> will append to the contents of a file.

Redirect the output of the ls command to a file called dirlist:

ls > dirlist

Append the date to the end of the file dirlist:

date >> dirlist


I introduced the concept of absolute and relative paths in section 2.3. In this session, the goal is to revisit paths (locations of files and directories in the filesystem), and provide some examples. This will be important as we proceed to Bash scripting and other tasks going forward.

Change Directories

The cd command is used to change directories. When we login to our systems, we will find ourselves in our $HOME directory, which is located at /home/USER.

To change to the root directory, type:

cd /

From there, to change to the /bin directory:

cd bin

To change to the previous working directory:

cd -

To go home quickly, just enter cd by itself:


To change to the public_html directory:

cd public_html

To change to the directory one level up:

cd ..
cd /home/sean

Make Directories

Sometimes we'll want to create new directories. To do so, we use the mkdir command.

To make a new directory in our $HOME directory:

mkdir documents
cd documents

To make more than one directory at the same time, where the second or additional directories are nested, use the -p option:

mkdir -p photos/2022

Remove or Delete Files and Directories

To remove a file, we use the rm command. If the file is in a subdirectory, specify the relative path:

rm public_html/index.html

To remove a file in a directory one level up, use the .. notation. For example, if I'm in my documents directory, and I want to delete a file in my home (parent) directory:

cd documents
rm ../file.txt

Alternatively, I could the tilde as shorthand for $HOME:

rm ~/file.txt

To remove a file nested in multiple subdirectories, just specify the path (absolute or relative).

rm photos/2022/05/22/IMG_2022_05_22.jpg

Remember that the rm command deletes files and directories. Use it with caution, or with the -i option.

Copy Files or Directories

Let's say I want to copy a file in my $HOME directory to a nested directory:

cp file.txt documents/ICT418/homework/

Or, we can copy a file from one subdirectory to another. Here I copy a file in my ~/bin directory to my ~/documentsdirectory. The ~ (tilde) is shorthand for my $HOME directory.

cp ~/bin/file.txt ~/documents/``

Move or Rename Files or Directories

Let's say I downloaded a file to my ~/Downloads directory, and I want to move it to my ~/documents directory:

mv ~/Downloads/article.pdf ~/documents/

Or, let's say we rename it in the process:

mv ~/Downloads/article.pdf ~/documents/article-2022.pdf

We can also move directories. Since the commandline is case-sensitive, let's say I rename the documents directory to Documents:

mv ~/documents ~/Documents


Use this page as a reference to the commands that we have covered so far.