Gain insights into the power of the command line. Learn about Linux BASH through theoretical and practical exercises, mastering essential concepts and commands for efficient programming.

Ever wondered why command line is still in use even when there are hundreds of human-friendly GUI’s and tools available? Everyone in the programmer's world would agree on one thing: Command Line is far more powerful than any GUI. It provides a richer experience in terms of speed and expressiveness.

For beginners, it might be hard to appreciate its beauty and a little challenging to shift from an interactive interface to a blank box with just a “$” sign showing that keeps prompting the user to enter complex commands if you want to get something done. This is why we felt the need to build a course which could help the user overcome his/her fear of using the terminal (we have all been there).

The objective of this course is to help you get a strong grip over Linux, mainly focusing on BASH. You will be covering both, the theoretical and practical sides. First, you will learn a bunch of concepts necessary to understand things and then study some nifty commands to get useful things done out of them.

Bash for Programmers

# chmod
## Definition: 
`chmod` command is short for "change mode", is typically used to change the read/write permissions of files and directories. A mode can either be represented symbolically with unique alphabets or by the permutations of three numbers (octal numbers) as we discussed in the previous lesson. We can also add references in the command to indicate the users on which the specified permissions are being applied. Given below is the syntax to `chmod` command.

## Syntax: 
```
chmod [references] [options] [mode] [file_name]
```


## Operators 

| **Operator** | **Meaning** |
| --- | --- |
| + | Adds the specified permissions on the files |
| - | Removes the specified perfmissions on the files |
| = | Add ONLY specified permissions on the file and remove the remaining permissions/modes |

## References 
References are basically used to indicate the users on which the permissions are applied. 
| **Reference** | **Meaning** |
| --- | --- |
| u | User who owns the file(s) |
| g | Users in the file group |
| o | Users which are neither owner of the file nor in the file group |
| a | All users. Same as `ugo` |


## Options 

| **Option** | **Meaning** |
| --- | --- |
| -f | suppress error messages |
| -v | outputs the file being processed |
| -c | to output warnings before making any changes |
| -R | Means *Recursive*. This option is used to change directories recursively |

## Example: 

1. You can set permissions by writing combination of three digit numbers where first digit is to set permission for the owner, second digit is to set permissions for the file group members, and third is to set permissions for other users. OR you can explicity write it as:

`chmod u=rw,g=wx,o=r my_file.c`

The numerical equivalent for this same command where owner can read and write the file, group members and write and execute the file and other users can only read the file:

`chmod 634 my_file.c`


2. To remove the permission of "execute" for a file for everyone:

`chmod a-x my_file.txt`

3. Allow other users to execute and read the file

`chmod o+rx my_file.txt`

This lesson will be covering the command that assists in setting or removing permissions.

Introduction to Bash

Navigation Commands

File Manipulation Commands

Permission Commands

Filtering & Searching Commands

System & Process Commands

Variables and Environment

An Overview of Commands

Set/Remove Permissions in Bash

chmod

Definition: