A Few Handy Commands in Linux (Part 1)

My first experience with using Linux was in 2017 when my Windows machine crashed and I lost all my files because silly me had no backup. Prior to that, I always wanted to use Linux just because I thought working with the command line would look rather cool and that was my chance for a fresh start I switched to Linux and never really looked back… well up until I could afford a MacBook.

Recently I took a keen interest in learning more about dev operations as a result, I took somewhat of a Linux refresher course so, I will be sharing things I learn and hopefully, this helps you learn something new.

The commands I will be sharing are basic commands that you would use frequently in Linux, I am not aiming to just share commands but ones that you most likely have to use at some point.

pwd Command

The pwd Command stands for print working directory. It is one of the most basic and frequently used commands in Linux. When invoked the command prints the absolute path of the current working directory. So if you are unsure of where you are in the command line pwd Command solves that for you.

ls Command

ls is one of the basic commands that any Linux user should know. The ls command lists files and directories within the file system and shows detailed information about them.

The syntax for the ls command is as follows:

ls [OPTIONS] [DIRECTORY]

When used with no options and arguments, ls displays a list of the names of all files in the current working directory:

The files are listed in alphabetical order in as many columns as can fit across your terminal.

To list files in a specific directory, pass the directory path as an argument to the ls command. For example, to list the contents of the /etc directory, you would type:

Using Options in ls Command

ls -l

The default output of the ls command shows only the names of the files and directories, which is not very informative. The -l ( lowercase L) option tells ls to print files in a long listing format showing more relevant information

Let’s make sense of the information provided above:

The file type i.e l — Type link, dr — Type directory respectively
The file permissions i.e r-read, w-write,x-execute
Number of hard links to the file.
File owner.
File group.
File size.
Date and Time.
Filename.

ls -a

By default, the ls command will not show hidden files. In Linux, a hidden file is any file that begins with a dot (.). To display all files including the hidden files use the -a option:

Absolute vs Relative Path Names

An absolute path is defined as specifying the location of a file or directory from the root directory(/) while A Relative path is defined as the path related to the present working directly(pwd), this means it doesn’t point directly to the root directory(/)

cd — Change Directory

The cd (“change directory”) command is used to change the current working directory in Linux and other Unix-like operating systems. It is one of the most basic and frequently used commands when working on the Linux terminal.

Absolute and Relative Paths

Other Relevant Directory

cd ../ (Parent Directory or one level up current dir)
cd ../../ ( two levels up current dir)
cd - (Previous Dir)
cd / (Root Dir)
cd ~ (Home Dir)

mkdir Command

The syntax for the mkdir command is as follows:

mkdir [OPTION] [DIRECTORY]

The command takes one or more directory names as its arguments.

mkdir newdir

When providing only the directory name, without the full path, it is created in the current working directory. To create a directory in another location you’ll need to provide the absolute or relative file path to the parent directory. For example, to create a new directory in the /home directory you would type:

mkdir /home/newdir

Create Parent Directories

A parent directory is a directory that is above another directory in the directory tree. To create parent directories, use the -p option.

Let’s say you want to create a directory /home/bryan/countries/Scotland:

mkdir /home/bryan/countries/Scotland

If any of the parent directories don’t exist you will get an error as shown below:

mkdir: cannot create directory '/home/bryan/countries/Scotland': No such file or directory

Instead of creating the missing parent directories one by one, invoke the mkdir command with the -p option:

mkdir -p /home/bryan/countries/Scotland

When the -p option is used, the command creates the directory only if it doesn’t exist.

Create Multiple Directories

To create multiple directories, specify the directories’ names as the command arguments, separated by space:

mkdir dir1 dir2 dir3

cp Command

cp is a command-line utility for copying files and directories on Unix and Linux systems.

How to Use cp command

The general syntax for the cp command is as follows:

cp [OPTIONS] SOURCE... DESTINATION

The SOURCE can contain one or more files or directories as arguments, and the DESTINATION argument can be a single file or directory.

• When the SOURCE and DESTINATION arguments are both files, the cp command copies the first file to the second one. If the file doesn’t exist, the command creates it.
• When the SOURCE has multiple files or directories as arguments, the DESTINATION argument must be a directory. In this situation, the SOURCE files and directories are moved to the DESTINATION directory.
• When the SOURCE and DESTINATION arguments are both directories, the cp command copies the first directory into the second one.

To copy files and directories, you must have at least read permissions on the source file and write permission on the destination directory. Otherwise, a permission denied error is shown.

Copying Files with cp Command

The most basic scenario of using cp is to copy a file in the current working directory . For example, to copy a file named file.txt to file_backup.txt, you wound run the following command:

cp file file_backup

To copy a file to another directory, specify the absolute or the relative path to the destination directory.

When only the directory name is specified as a destination, the copied file has the same name as the original file.

In the following example, we are copying the file file.txt to the /backup directory:

cp file.txt /backup

If you want to copy the file under a different name, you need to specify the desired file name. The command below will copy the file to the specified directory as new_file.txt.

cp file.txt /backup/new_file.txt

By default, if the destination file exists, it is overwritten. The -n option tells cp not to overwrite an existing file.

Copying Directories with cp Command

To copy a directory, including all its files and subdirectories, use the -R or -r option.

In the following example, we are copying the directory Pictures to Pictures_backup:

cp -R Pictures Pictures_backup

Copy Multiple Files and Directories

To copy multiple files and directories at once, specify their names and use the destination directory as the last argument:

cp file.txt dir file1.txt  dir1

When copying multiple files, the destination must be a directory.

mv Command

How to Use the mv Command

The mv command (short from move) is used to rename and move and files and directories from one location to another. The syntax for the mv command is as follows:

mv [OPTIONS] SOURCE DESTINATION

The SOURCE can be one, or more files or directories, and DESTINATION can be a single file or directory.

• When multiple files or directories are given as a SOURCE, the DESTINATION must be a directory. In this case, the SOURCE files are moved to the target directory.
• If you specify a single file as SOURCE, and the DESTINATION target is an existing directory, then the file is moved to the specified directory.
• If you specify a single file as SOURCE, and a single file as DESTINATION target then you’re renaming the file.
• When the SOURCE is a directory and DESTINATION doesn’t exist, SOURCE will be renamed to DESTINATION. Otherwise if DESTINATION exist, it be moved inside the DESTINATION directory.

For example, to move the file file1 from the current working directory to the /tmp directory you would run:

mv file1 /tmp

To rename a file you need to specify the destination file name:

mv file1 file2

The syntax for moving directories is the same as when moving files. In the following example, if the dir2 directory exists, the command will move dir1 inside dir2. If dir2 doesn’t exist, dir1 will be renamed to dir2:

mv dir1 dir2

Moving Multiple Files and Directories

To move multiple files and directories, specify the files you want to move as the source. For example, to move the files file1 and file2 to the dir1 directory you would type:

mv file1 file2 dir1

The mv command also allows you to use pattern matching. For example, to move all pdf files from the current directory to the ~/Documents directory, you would use:

mv *.pdf ~/Documents

Cat Command

The name of the cat command comes from its functionality to concatenate files. It can read, concatenate, and write file contents to the standard output.

cat Command Syntax

Before going into how to use the cat command, let’s start by reviewing the basic syntax.

The cat utility expressions take the following form:

cat [OPTIONS] [FILE_NAMES]

Displaying File Contents

The most basic and common usage of the cat command is to read the contents of files.

For example, the following command will display the contents of the /etc/yum.conf file on the terminal:

cat /etc/yum.conf

Redirect Contents of File

Instead of displaying the output to stdout (on the screen), you can redirect it to a file.

The following command will copy the contents of file1.txt to file2.txt using the (>) operator :

cat file1.txt > file2.txt

Normally you would use the cp command to copy a file.

If the file2.txt file doesn’t exist, the command will create it. Otherwise, it will overwrite the file.

Use the (>>) operator to append the contents of file1.txt to file2.txt :

cat file1.txt >> file2.txt

Same as before, if the file is not present, it will be created.

Creating Files

Creating small files with cat it often easier than opening a text editor such as nano, vim, visual studios.

To create a new file, use the cat command followed by the redirection operator (>) and the name of the file you want to create. Press Enter, type the text and once you are done, press the CRTL+D to save the file.

In the following example, we are creating a new file named file1.txt:

cat > file1.txt

touch Command

In its simplest form when used without any options, if the file name specified as an argument doesn’t exist touch will create a new file.

If the file already exists touch will change the file's last access and modification times to the current time.

For example, if the file file1 doesn’t exist the following command will create it otherwise, it will change its timestamps:

touch file1

rm Command

rm is a command-line utility for removing files and directories. It is one of the essential commands that every Linux user should be familiar with.

How to Use the rm Command

The general syntax for the rm (remove) command is as follows:

rm [OPTIONS]... FILE...

By default, when executed without any option, rm doesn’t remove directories and doesn’t prompt the user for whether to proceed with the removal of the given files.

To delete a single file, use the rm command followed by the file name as an argument:

rm filename

If you don’t have write permissions on the parent directory, you will get an “Operation not permitted” error.

If the file is not write-protected, it will be removed without notice. On success, the command doesn’t produce any output and returns zero.

When removing write-protected files, the command will prompt you for confirmation, as shown below:

rm: remove write-protected regular empty file 'filename'?

Type y and hit Enter to remove the file.

The -f option tells rm never to prompt the user and to ignore nonexistent files and arguments.

rm -f filename

If you want to get information about what is being removed, use the -v (verbose) option:

rm -v filename
removed 'filename'

Removing Multiple Files

rm allows you to delete multiple files at once. To do that, pass the filenames as arguments separated by space:

rm filename1 filename2 filename3

You can use regular expressions to match multiple files. For example, to remove all .png files in the current directory, you would type:

rm *.png

When using regular expressions, before running the rm command. is always a good idea to list the files with the rmcommand so that you can see which files will be deleted.

Removing Directories (Folders)

To remove one or more empty directories use the -d option:

rm -d dirname

To remove non-empty directories and all the files within them recursively, use the -r (recursive) option:

rm -r dirname

I figured this was getting a bit long so I decided to make a 2-part article. I hope you learnt something relevant. Thanks for reading.