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| 1 | + | The **`PATH`** shell variable in the Bash shell is a special environment variable that tells your | |
| 2 | + | system **where to look for executable programs** when you type a command. | |
| 3 | + | ||
| 4 | + | ### Why is it needed? | |
| 5 | + | When you type a command like `ls` or `python`, the system doesn’t magically know where that | |
| 6 | + | program or script is stored. Instead, it searches through a list of directories (folders) defined | |
| 7 | + | in the **`PATH`** variable to find the executable file. | |
| 8 | + | ||
| 9 | + | --- | |
| 10 | + | ||
| 11 | + | ### How does `PATH` work? | |
| 12 | + | 1. **The `PATH` is a list of directories**: | |
| 13 | + | The `PATH` variable contains multiple directory paths separated by colons `:`. For example: | |
| 14 | + | ``` | |
| 15 | + | /usr/local/bin:/usr/bin:/bin:/home/user/bin | |
| 16 | + | ``` | |
| 17 | + | 2. **Command Search**: | |
| 18 | + | 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. | |
| 19 | + | ||
| 20 | + | 3. **If Found**: It runs the program. | |
| 21 | + | **If Not Found**: Bash returns a "command not found" error. | |
| 22 | + | ||
| 23 | + | --- | |
| 24 | + | ||
| 25 | + | ### Example for Beginners | |
| 26 | + | - Suppose your `PATH` looks like this: | |
| 27 | + | ``` | |
| 28 | + | /usr/local/bin:/usr/bin:/bin | |
| 29 | + | ``` | |
| 30 | + | - You type `python`. | |
| 31 | + | - Bash will look for an executable named `python` in: | |
| 32 | + | - `/usr/local/bin` | |
| 33 | + | - `/usr/bin` | |
| 34 | + | - `/bin` | |
| 35 | + | - If it finds `python` in `/usr/bin`, it stops searching and runs it. | |
| 36 | + | ||
| 37 | + | --- | |
| 38 | + | ||
| 39 | + | ### Why is `PATH` Useful? | |
| 40 | + | - It allows you to **run commands without typing the full path** to the executable. | |
| 41 | + | For example, instead of: | |
| 42 | + | ``` | |
| 43 | + | /usr/bin/python3 | |
| 44 | + | ``` | |
| 45 | + | You can simply type: | |
| 46 | + | ``` | |
| 47 | + | python3 | |
| 48 | + | ``` | |
| 49 | + | - It lets you add custom directories to prioritize or include your own scripts or programs. | |
| 50 | + | ||
| 51 | + | --- | |
| 52 | + | ||
| 53 | + | ### Adding a Directory to `PATH` | |
| 54 | + | To add a directory (e.g., `/home/user/scripts`) to your `PATH`: | |
| 55 | + | ```bash | |
| 56 | + | export PATH=$PATH:/home/user/scripts | |
| 57 | + | ``` | |
| 58 | + | Now, any executable in `/home/user/scripts` can be run directly by typing its name. | |
| 59 | + | ||
| 60 | + | --- | |
| 61 | + | ||
| 62 | + | In short, the `PATH` variable makes it convenient and efficient to execute programs without | |
| 63 | + | needing to type out their full file locations every time. It's like a **"search roadmap"** | |
| 64 | + | for your system to find commands. | |
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