Script Koder

Posted on Sep 12 • Edited on Sep 23

Working With Shell

#bash #beginners #tutorial #linux

What is a shell?

Linux shell is a program that allows text-based interaction between the user and the computer

Types of shell in Linux

Linux Commands

Linux command consists of program name followed by the option and arguments.
For ex.

cat -n myfile

# program name: cat
# option: -n
# argument: myfile

Home directory

The home directory is a directory that stores user-specific data.
this data can be of any type
for ex. If there is a user named john, then john's data like images, documents, downloads, etc. data will reside in /home/john/ location

How to know the Home directory

echo $HOME
# This command will read from the environment variable $HOME

echo ~
# This command will expand the tilde symbol to the given user's home directory path

Directory Management

How to know your current path

To know the current path, we use the command pwd, which stands for Present working directory

pwd

How to create & remove directories

mkdir is a command that is used to create a directory
rmdir is a command that is used to delete an empty directory
example

# to create a directory
mkdir test_directory

# to create multiple directories
mkdir test1 test2 test3

# to delete a directory
rmdir test_directory

# to remove multiple directories
rmdir test1 test2 test3

How to list the content of a folder

to list the content of a directory we use the ls command

# to list the content of a directory
ls

How to create a chain of directories

in order to perform this we use the "-p" parameter with mkdir command
Example

# We want to create 4 directories each inside of it's parent directory
mkdir -p a/b/c/d

How to navigate through directories

To switch directories we use cd command

# Changing to the parent directory
cd ../

# Changing to the home directory
cd /home/user1

How to navigate folder directory in Linux

there are two types of path notation in Linux
1. Relative Path
2. Absolute Path

Relative path

relative path is defined with respect to the current directory
"." represents the current working folder
".." represents the parent directory
For example

# to change to the parent directory for the current directory
cd ../

# to run a file/script present in the current directory
bash ./example.sh

Absolute path

absolute paths are defined with respect to the root "/" location
for example

# navigating to the user1 document folder
cd /home/user1/documents

PUSHD & POPD

pushd and popd commands are used to manage the directory stack.
Example

# we created 3 directories
mkdir -p a/b/c

# now we navigate to c directory using pushd command, by pushing it's path to directory stack
pushd a/b/c

# this command will take us to the given c directory and we can create a file here
echo "hello world" > test_file.txt

# to navigate to the previous path we can use popd command
# this will bring us to the parent directory
popd

Top comments (13)

Jimmy McBride • Sep 13

Would love to see something about pushd and popd in addition to cd. They can be very handy tools when you changing directories a lot and need to make a quick escape to where you've previously been! :)

Can't wait to see more!

Script Koder • Sep 13

Thanks for your response, i'll keep updating this page.

BC • Sep 13

I think an important concept is also where a user's shell is defined.

A user's shell is typically setup when the user is added to the system. Often /bin/bash is set as a default, but macOS now sets /bin/zsh as the default shell for users.

A user could find their default shell by viewing the /etc/passwd file. For example,

root:x:0:0:root:/root:/bin/bash
games:x:12:100:games:/usr/games:/sbin/nologin

In the above example root's default shell is set to the Bash shell. While the games user actually has been set to a nologin shell, preventing anyone from logging into the user. This has certain uses for non-interactive user sessions. We have other shell options that we can use as well. There are lots of varieties and it depends on your OS, or what the administrator has set at account creation.

There are different commands to modify a user's shell. But one way you can do this is with the usermod command:

usermod -s /bin/bash USER

If you want to find a list of available shells on your system, try this command:
cat /etc/shells

Paul J. Lucas • Sep 13

There's no such thing as a Linux shell. There are only various shells, e.g., bash, tcsh, zsh, etc. You can use exactly the same shells on FreeBSD, macOS, and others as you can on Linux.

Script Koder • Sep 13 • Edited

@pauljlucas Yeah, you are correct mate, thanks for the help, i've updated the title accordingly.

Paul J. Lucas • Sep 13

You might want to reconsider the banner image and #linux tag as well.

Paul J. Lucas • Sep 15

You still mention "Linux shell....". You ought to replace that with "A shell...."

Script Koder • Sep 13

sure, i'm working on it

Mike Stemle • Sep 16

I’m glad to see folks still talking about the terminal. That said, none of this is bash-specific. These will all work in a variety of shells, and I hope folks find whatever shell they prefer and have a great time in the shell.

Paul J. Lucas • Sep 15

You mention commands, but never once mention the PATH environment variable or explain that commands like mkdir "live" in certain directories and the way commands work is that the shell searches PATH for a matching command.

Khaled Md Saifullah • Sep 14

In my opinion "how bash works" is also an important topic for a beginners, Don't you think so?

Script Koder • Sep 14

Beginners with no experience with bash, see the black screen and don't know what to write on it.

From my Teaching experience, they are more interested in, How to use it.
not "How it works".

I hope you understood my point, sir.

Thanks for your Feedback though

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