> ## Documentation Index
> Fetch the complete documentation index at: https://notes.kodekloud.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Dash
> This article explains the `$-` special shell variable in Bash, detailing its flags and differences between interactive and non-interactive modes.
The `$-` variable in Bash shows the current shell’s option flags. These flags differ when you run commands interactively versus inside a script. In this guide, we’ll:
* Inspect `$-` interactively
* Compare interactive vs. non-interactive outputs
* Demonstrate how `set -e` affects `$-`
* Review common `$-` flags in a summary table
***
## Checking `$-` Interactively
Run the following command in your terminal to see which flags are active in your interactive shell:
```bash theme={null}
echo $-
```
Example output:
```bash theme={null}
himBHs
```
Each letter (such as `h`, `i`, `m`, `B`, `H`, `s`) represents a specific shell option. These may vary between systems and user configurations.
The exact set of flags depends on your Bash version and how you’ve configured your environment (e.g., via `.bashrc` or `.bash_profile`).
***
## Comparing with a Non‐Interactive Script
Create a file named `special-dash.sh`:
```bash theme={null}
#!/usr/bin/env bash
echo $-
```
Make it executable and run it:
```bash theme={null}
chmod +x special-dash.sh
./special-dash.sh
```
Typical output:
```bash theme={null}
hB
```
You’ll notice the `i` flag (interactive mode) is missing because scripts run non-interactively by default.
***
## Enabling “Exit on Error” with `set -e`
The `set -e` option causes Bash to exit immediately if any command returns a non-zero status. Let’s enable it in our script:
```bash theme={null}
#!/usr/bin/env bash
set -e
echo $-
```
Run the updated script:
```bash theme={null}
./special-dash.sh
```
Now you should see:
```bash theme={null}
ehB
```
The leading `e` indicates that “exit on error” is active.
Using `set -e` can make debugging harder if you’re not careful. Always test scripts thoroughly or combine with `set -u` and `set -o pipefail` for stricter error checking.
***
## Common `$-` Flags
| Flag | Description |
| ---- | -------------------------------------------------- |
| i | Shell is running in interactive mode |
| e | Exit immediately if a command exits with failure |
| u | Treat unset variables as an error |
| x | Print commands and their arguments as they execute |
***
## Further Reading
* [Bash Reference Manual – Invocations](https://www.gnu.org/software/bash/manual/html_node/Invocations.html)
* [Bash Scripting Guide](https://tldp.org/LDP/Bash-Beginners-Guide/html/)
***
By understanding and inspecting the `$-` variable, you can better control your shell’s behavior in both interactive sessions and automated scripts.