Shell execution commands — source bash and dot

The note is generated by “ChatGPT”.

🔹 source

• Executes a script in the current shell environment.
• Does not create a new shell process.
• All variable exports, alias definitions, and PATH modifications remain active after execution.
• Commonly used for reloading configuration files (e.g., source ~/.bashrc).
• Bash and Zsh built-in command.

Example:

1

source ~/.bashrc

→ Reloads your Bash configuration immediately in the current session.

🔹 bash

• Starts a new Bash subshell to run the script.
• The parent shell does not inherit any environment changes.
• Safer for running scripts that should not affect your current session.
• Suitable for installation, automation, or isolated execution.

Example:

1

bash install.sh

→ Runs the script, but changes (like export PATH=...) disappear when it exits.

🔹 .

• A POSIX-standard alias for source.
• Works in all POSIX-compliant shells (e.g., sh, dash, bash, zsh).
• Functionally identical to source.

Example:

1

. ~/.bashrc

→ Same as source ~/.bashrc, but more portable across shells.

⚙️ Comparison Table

🧠 Quick Example

1
2
3

# test.sh
export MYVAR="Hello"
echo "Inside script: $MYVAR"

Run it two ways:

1
2

bash test.sh     # MYVAR not available after run
source test.sh   # MYVAR stays in current shell

✅ Key Takeaway

• Use bash when you want isolation.
• Use source or . when you want persistent changes in your shell session.