She Bang #! /bin/bash

The line: #! /bin/bash

#! /bin/bash

is called a shebang (or hashbang). It tells the system which interpreter should be used to execute the script.

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🔍 If you include #!/bin/bash at the top of script.sh:

• You're explicitly saying: "Use the Bash shell to run this script."

• You can execute it directly like this:

    ./script.sh
  

  (as long as you’ve done chmod +x script.sh to make it executable)

• The system will invoke /bin/bash to interpret the script.

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❌ If you omit #!/bin/bash:

• The script might still work, but:

  • It will be run using the default shell defined in your environment (often /bin/sh).

  • /bin/sh is not always bash. On some systems, it's a different shell like dash, which is faster but less feature-rich.

  • Any Bash-specific syntax (like [[ ]], arrays, etc.) may break or behave differently.

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✅ Best Practice:

Always use the shebang line to avoid ambiguity and ensure your script behaves consistently across systems.

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Quick Example:

#!/bin/bash
echo "This is Bash-specific"

If this script uses Bash features and you run it without a shebang (or with sh script.sh), it might throw errors or misbehave.