Shebang / chmod +x

Shebang. Declares that this script should be run with /bin/bash.

#!/bin/bash

Finds bash via env (portable style that avoids hard-coded paths).

#!/usr/bin/env bash

Grant execute permission to a script.

chmod +x script_filename

Run directly (shebang required).

./script_filename

Run with the bash command (no shebang or execute permission needed).

bash script_filename

Shebang / Command	Description
#!/bin/bash	Runs with the Bash shell. The most common form.
#!/usr/bin/env bash	Finds bash via PATH and runs it. Recommended for macOS and nvm environments.
#!/bin/sh	Runs with a POSIX-compliant shell. Use this when maximum portability is the priority.
#!/usr/bin/env python3	Runs with Python 3.
#!/usr/bin/env node	Runs with Node.js.
#!/usr/bin/env php	Runs with PHP.
chmod +x file	Grants execute permission to all users.
chmod 755 file	Grants rwx to the owner and r-x to group and others.
chmod 700 file	Grants execute permission to the owner only (others cannot execute).

Create a file called hello.sh with the following content.

hello.sh

#!/usr/bin/env bash
# hello.sh — A basic shell script template

echo "Script name: $0"
echo "Number of arguments: $#"
echo "All arguments: $@"

if [ $# -eq 0 ]; then
    echo "Usage: $0 name" >&2
    exit 1
fi

echo "Hello, $1!"

Grant execute permission to the script.

chmod +x hello.sh

Checking the permissions, you can see that x (execute permission) is now set.

ls -l hello.sh
-rwxr-xr-x 1 user user 42 Mar  6 12:00 hello.sh

With the shebang and execute permission in place, you can run the script directly using ./.

./hello.sh Alice
Script name: ./hello.sh
Number of arguments: 1
All arguments: Alice
Hello, Alice!

When running with the bash command, neither execute permission nor a shebang is required.

bash hello.sh Bob
Script name: hello.sh
Number of arguments: 1
All arguments: Bob
Hello, Bob!

The shebang must be written on the first line of the file. A blank line or BOM (Byte Order Mark) before it will make it ineffective. To avoid environment-specific issues, the #!/usr/bin/env bash form is recommended.

chmod +x marks a file as executable. Running a script with ./ requires execute permission, but specifying the interpreter explicitly — as in bash script_name — works without it. See also Special Variables for details on how variables and arguments are handled inside scripts.