# alias  commands in Linux

In Linux, an `alias` is a command that executes another command or series of commands using a different name. Aliases are typically used to make it easier to run frequently used or complex commands by typing a shorter, easier-to-remember version. The alias command takes the following structure:

```bash
alias [alias-name]='[command]'
```

* `alias`: Invokes the `alias` command.
    
* `alias-name`: An alias is a user-defined string that acts as a reference to a command, with the exception of certain special characters and the words 'alias' and 'unalias'.
    
* `command`: Specifies the command the alias references.
    

For example:

1. `alias ll='ls -al'`: This alias creates a new command called `ll` that is equivalent to running the `ls -al` command. You could use this alias to list the contents of a directory in long format by typing `ll` instead of `ls -al`.
    
2. `alias df='df -h'`: This alias creates a new command called `df` that is equivalent to running the `df -h` command. The `-h` flag is used to display the sizes of files in "human-readable" format (e.g., in MB or GB instead of bytes).
    
3. `alias grep='grep --color=auto'`: This alias creates a new command called `grep` that is equivalent to running the `grep --color=auto` command. The `--color=auto` flag tells `grep` to highlight the matching text in the output, making it easier to spot.
    
4. `alias shutdown='sudo shutdown -h now'`: This alias creates a new command called `shutdown` that is equivalent to running the `sudo shutdown -h now` command. The `-h` flag tells the `shutdown` command to halt the system, and the `now` argument tells it to do so immediately.
    
5. `alias update='sudo apt update && sudo apt upgrade -y'`: This alias creates a new command called `update` that is equivalent to running the `sudo apt update` and `sudo apt upgrade -y` commands. The `update` command updates the package manager's list of available packages, and the `upgrade` command installs any available updates for installed packages. The `-y` flag tells `apt` to assume "yes" as the answer to all prompts.
    

A few ways I use the alias command in my day to day development:

### Copying trading bots from `wine` to my documents.

I currently work on Linux but need to do MQL5 programming from time to time. With MQL5, I can write trading bots for clients. However, to compile the MQL5 code to an `.ex5` executable, I need to have MT5 installed. MT5 is a Windows and Mac program; therefore, I have to install `wine` on Linux. `Wine` is a compatibility layer that allows you to run Windows applications on Linux. It does this by translating the Windows application's calls into calls that the Linux operating system can understand and processing them on behalf of the application. This allows you to run Windows applications on Linux without installing a copy of the Windows operating system. Once the code is compiled into an executable, the files are stored in the `wine` drive. To copy the `.ex5` to a specific folder, I would normally run the following command

```bash
cd /home/wamaitha/.wine/drive_c/Program\ Files/Deriv/MQL5
```

The `MQL5` directory has a folder that holds all the trading bots I program. Therefore, I can copy all the `.ex5` files to the `EAS` folder with the command below.

```bash
cp -r Experts/**/*.ex5 ~/Documents/FOREX/EAS
```

To make my work easier, I've written an alias command that does all this

```bash
alias fxeas="cd /home/wamaitha/.wine/drive_c/Program\ Files/Deriv/MQL5 && cp -r Experts/**/*.ex5 ~/Documents/FOREX/EAS"
```

### Activating virtual environments

In Python when using `virtualenv` , to activate the environment on Linux we need to type the following command:

```bash
source venv/bin/activate
```

Then navigate back to the project folder

```bash
cd .. && cd ..
```

We can write an `alias` for this

```bash
alias activate="source venv/bin/activate && cd .. && cd .."
```

### Permanent aliases

Using the `alias` command only applies to the current terminal session. To make the commands useful on other terminal sessions, you would need to edit the `.bashrc` file if running `bash` or the `.zshrc` if on `zsh`. I'm currently on `zsh` , therefore I add these commands at the end of the `.zshrc` file.

Launch the `.zshrc` using the command below

```bash
nano ~/.zshrc
```

Add the `alias` commands at the end of the file

```bash
alias activate="source venv/bin/activate && cd .. && cd .."
alias fxeas="cd /home/wamaitha/.wine/drive_c/Program\ Files/Deriv/MQL5 && cp -r Experts/**/*.ex5 ~/Documents/FOREX/EAS"
```

Run the command below to activate the changes for all terminal sessions.

```bash
source ~/.zshrc
```