Useful Shell Commands

for your daily linux hacking

Easy Shell is a collection of useful boilerplate linux commands for the daily life of every linux user!

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Hey you!

This is a “go through” guide intended to help newcomers and medium Linux users on consulting useful bash commands.

This is a living web page! Which means it will be updated on a regular basis as more and more people contribute to it :)

This is not a guide, nor a tutorial for Linux, Shell or Bash. For reals. It’s just a collection of some good commands, materials, tips and tricks gathered from all around the internet and presented in a nice way so you can easily find it.

Thank you and keep bashing!


Introduction: basic linux knowledge

  • This is probably the most important lesson you will ever learn on Linux: man pages are your best friend! Learn to read them. Learn to understand them. Learn to love them.

To access a man page on any linux program just type:

$ man <program>


$ man ps
PS(1)                                        User Commands                                       PS(1)

       ps - report a snapshot of the current processes.

       ps [options]

       ps displays information about a selection of the active processes.  If you want a repetitive
       update of the selection and the displayed information, use top(1) instead.

       This version of ps accepts several kinds of options:

       1   UNIX options, which may be grouped and must be preceded by a dash.
       2   BSD options, which may be grouped and must not be used with a dash.
       3   GNU long options, which are preceded by two dashes.
  • To view a short information on any program:

$ whatis <program>

  • You can also find out where it is located by typing:

$ whereis <program>

  • To change user:

$ sudo -u <user>

  • To change user to superuser (root):

$ sudo su

Attention: This is not recommended since as a superuser you have total control of your system, hence you can end up fucking it badly.

  • ”/” represents the root directory.

  • ”~” is an alias for your user’s home directory, which usually is: /home/youruser/.

  • ”.” represents the current directory

  • To decompress a tarball:

tar -vzx <compressed-file.tar.gz>

Note: Flag -v is for verbosity.

  • To see your session history:


Pretty useful stuff:

  • | is a piping operator. It is used for inserting the output of a program into the input of another program.


Listing all process called “init”:

ps -aux | grep init

  • You can quickly write something into a file by doing:

echo "any random sentence" >> any-random-file.txt

The ‘»’ operator will concatenate the sentence to the end of the file.

BE CAREFUL not to use ‘>’ instead of ‘»’ since the former will OVERWRITE the content of the file instead of adding the sentence to it.

  • You can call a previously used command pra typing “!” plus the initials of the said program.

For example, let us say you want to edit .bashrc and then open it to edit again:

vim ~/.bashrc
exec bash
!vim #This will execute the last command on history with the "vim" initials
  • uname -a will tell you information about your system

  • df -h will tell you about your file system disk space


Working with files

  • Where am I?

$ pwd

  • Creating Files

$ > filename

  • Changing directories

$ cd path/to/directory

  • Moving things around

$ mv -v <filename> /another/path/

  • Deleting things FOREVER

sudo mv -v <filename> /dev/null/

  • Copying stuff

$ cp -v <filename> <another-filename>

  • Deleting files

$ rm -v <filename>

  • Deleting folders

$ rm -vR /path/to/<folder>

  • Updating timestamp:

$ touch <filename>

  • Listing files and directories

$ ls -al

Notes: - -a tells ls to list all files. - Files starting with . are hidden files. (Remember this).

  • Printing the content of a file:

cat <filename.txt>

  • Printing the last 2 lines of a file:

tail -n 2 <filename.txt>

  • Printing the first 2 lines of a file:

head -n 2 <filename.txt>


Working with environment and variables

Listing local variables

$ set

Listing global variables

$ env

Printing variable content

$ foo='This is a variable!'
$ echo $foo

Looking for a local variable

$ set | grep foo

Exporting it to env

$ export foo
$ env | grep foo

Useful environment variables

  • $PS1 your prompt setup
  • $PATH your path setup
  • $USER your current user

The most important files regarding your environment are:

  1. $ ~/.profile
  2. $ ~/.bashrc

Both of them are shell scripts and contain instructions which are executed when you log in.

Permanently exporting variables to your PATH:

`$ echo ‘export $PATH=”$PATH:/path/to/file/”’ » ~/.bashrc


Managing and killing processes

To list all processes on your system

$ ps -aux

To list all processes running as root

$ ps -U root -u root u

To list all processes owned by you

$ ps x

Searching processes by keyword

$ ps -aux | grep '<keyword>'

Listing it Tree style

$ ps -aux --forest

Killing a specific process

$ sudo kill -9 <PID>

Killing all processes except for kill and init

$ sudo kill -9 -1


File permissions

  • To change the owner of a directory:

    $ sudo chown -R newowner:newowner

  • To view actual files permissions

    $ ls -l

    • Example: drwxr-xr-x:
      • First letter is the file type:

        d b c p s -
        directory block file special file pipe socket regular file
      • Second, third and fourth letters are the user permissions
      • Fifth, sixth and seventh letters are the group permissions
      • Eighth, ninth and tenth letters are the others permissions
      • Permissions

        r w x -
        read write execute disable
  • To change the files permissions:

    • Using letters:
      • Which users:

        u g o a
        user group others all
      • Operators:

        + - =
        add permission remove permission changes permissions to the inserted
      • Permissions:

        r w x
        read write execute
      • Example: $ chmod a+w file add write permission for all users

    • Using numbers
      • Permissions:

        read write execute
        4 2 1
      • Example: $ chmod 754 file set permission to file:

        user group others
        7 5 4
        read + write + execute read + execute read


Search, save and simplify command outputs:

Bit bucket (as known as the black hole, one of the linux’s special files):


Standard input stream:


Standard outpout streams:


Tailing files (getting the last lines)

$ tail <file>

Outputing whole file content

$ cat <file>

Reading from STDIN to a file (stop with CTRL + C)

cat > <file>

Reading from file to another file

cat <file1> > <file2>

Reading all lines of file with line numbers

cat -n <file>

Saving output to file (using nano editor)

$ <command> | nano file_name

Searching through the output

$ <command> | grep <term>

Displaying output in a file-like style (less allows searching by pressing /)

$ <command>|less or $ <command>|more

Preventing terminal hanging (command outputs will still be shown in the terminal)

$ <command>&

Ignoring file output completely (note that 2 = STDERR and 1 = STDOUT)

$ <command> > /dev/null 2 > &1

Custom Bash

Custom Bash

Customize your bash cursor

The PS1 environment variable contains the style for the bash cursor:

Export it to your ~/.bashrc file:

export PS1='\u@\h \$'

This will print the following as a cursor: user@host $

Some formatting options can be:

\h - The hostname, up to the first ' . '

\H - The hostname.

\n - A newline.

\t - The time, in 24-hour HH:MM:SS format.

\T - The time, in 12-hour HH:MM:SS format.

\@ - The time, in 12-hour am/pm format.

\u - The username of the current user.

\w - The current working directory, with $HOME abbreviated with a tilde (uses the $PROMPT_DIRTRIM variable).

\W - The basename of $PWD, with $HOME abbreviated with a tilde.

Further reading:

PS1 Generator

Git info on bash PS1

Bash manual



Utils commands

Show all network interfaces

$ ifconfig

Configure a wireless network interface

$ iwconfig

Get more information about wireless interface

$ iwlist <your_interface_here> scan

Check hardware information include about your network, this shows PCIs drivers which is installed or not

$ lspci

Show who is connected in your network

$ nmap 192.168.0.*

Verify if you have any open port

$ nmap <your_ip>