Introduction to OS and Linux

What is an Operating System?

An operating system (OS) is a type of system software that controls how computer hardware and software resources are used and offer basic services to other software applications.

Examples: Microsoft Windows, Linux, Android, Unix, macOS etc.

What is LINUX?

The most popular and well-known open-source operating system is Linux. As an operating system, Linux is a piece of software that runs in the background of all other applications on a computer, taking requests from them and transmitting them to the hardware.

Some commands for Beginners

  • Clear the console

               clear

  • Changing Working Directory

            cd Desktop

             cd Home

  • List all files in a directory

                 ls

  • Copy all files of a directory within the current work directory

             cp dir/* .

  • Copy a directory within the current work directory

            cp -a tmp/dir1

  • To make an archive of existing folders or files

         tar cvf archive_name.tar          dirname/

         tar cvf alldocs.tar *.txt

  • Extract from an existing tar archive.

        tar xvf archive_name.tar

  • View an existing tar archive.

        tar tvf archive_name.tar

Basic command of UNIX/LINUX

Command and Description

 ls – Show files in the current position

 cd – Change directory

cp – Copy file or directory

mv– Move file or directory

rm – Remove file or directory

pwd – Show the current position

 mkdir – Create directory

rmdir – Remove directory

less, more, cat – Display file contents

man – Read the online manual page for a command

whatis – Give a brief description of a command

su – Switch user

passwdChange password

useradd – Create a new user account

userdel – Delete a user account

mount – Mount file system

 umount – Unmount file system

df – Show disk space usage

shutdown -Reboot or turn off machine

Compiling C/C++ program using g++ and gcc:

For C++:

Command: g++ source_files… -o output_file

For C:

Command: gcc source_files… -o output_file

Source files need not be cpp or c files. They can be preprocessed files, assembly files, or object files.

The whole compilation file works in the following way:

Cpp/c file(s)Preprocessed file(s)  Assembly File(s) Generation  Object file(s) Generation  Final Executable

Every c/cpp file has its own preprocessed file, assembly file, and object file.

1. For running only the preprocessor, we use

-E option.

2. For running the compilation process till assembly file generation, we use –S option.

3. For running the compilation process till object file creation, we use –c option.

4. If no option is specified, the whole compilation process till the generation of the executable will run.

A file generated using any option can be used to create the final executable. For example, let’s suppose that we have two source

files: math.cpp and main.cpp, and we create object files:

g++ main.cpp –c –o main.o

g++ math.cpp –c –o math.o

The object files created using above two commands can be used to generate the final executable.

g++ main.o math.o –o my_executable

The file named “my_executable” is the final exe file. There is a specific extension for executable files in Linux.

Conclusion

Linux operating system is very flexible. It can be used for desktop applications, embedded systems, and server applications too. In this article, I tried to explain how basic command of UNIX/LINUX basic command works and you will see the details of how to compile C/C++ programs using g++ and gcc, Trying to put more interesting content for you to stay updated 🙂
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