Shebang and Running Scripts

Updated September 2026 · Beginner-friendly guide

The shebang line

The first line tells the kernel which interpreter to use. env finds bash on your PATH.

#!/usr/bin/env bash
# hello.sh
echo "Hello"

Create the file, then chmod and run with a relative path.

chmod +x hello.sh
./hello.sh

Useful while testing: bash hello.sh does not require the executable bit.

bash hello.sh
bash -n hello.sh   # syntax check only

Scripts start in the caller's current directory unless you change it. Prefer locating files relative to the script when needed.

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
echo "$SCRIPT_DIR"

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