kristofer / The PATH variable in a shell

The **`PATH`** shell variable in the Bash shell is a special environment variable that tells your system **where to look for executable programs** when you type a command. ### Why is it needed? When you type a command like `ls` or `python`, the system doesn’t magically know where that program or script is stored. Instead, it searches through a list of directories (folders) defined in the **`PATH`** variable to find the executable file. --- ### How does `PATH` work? 1. **The `PATH` is a list of directories**: The `PATH` variable contains multiple directory paths separated by colons `:`. For example: ``` /usr/local/bin:/usr/bin:/bin:/home/user/bin ``` 2. **Command Search**: When you type a command, Bash searches through each directory in the `PATH` one by one (in order) to see if the command's executable file exists there. 3. **If Found**: It runs the program. **If Not Found**: Bash returns a "command not found" error. --- ### Example for Beginners - Suppose your `PATH` looks like this: ``` /usr/local/bin:/usr/bin:/bin ``` - You type `python`. - Bash will look for an executable named `python` in: - `/usr/local/bin` - `/usr/bin` - `/bin` - If it finds `python` in `/usr/bin`, it stops searching and runs it. --- ### Why is `PATH` Useful? - It allows you to **run commands without typing the full path** to the executable. For example, instead of: ``` /usr/bin/python3 ``` You can simply type: ``` python3 ``` - It lets you add custom directories to prioritize or include your own scripts or programs. --- ### Adding a Directory to `PATH` To add a directory (e.g., `/home/user/scripts`) to your `PATH`: ```bash export PATH=$PATH:/home/user/scripts ``` Now, any executable in `/home/user/scripts` can be run directly by typing its name. --- In short, the `PATH` variable makes it convenient and efficient to execute programs without needing to type out their full file locations every time. It's like a **"search roadmap"** for your system to find commands.