Your First Script

A script is a text file containing commands. Running it runs every command in order — so you only have to work something out once.

Writing it

Create a file called hello.sh in any text editor (VS Code, nano, vim):

#!/usr/bin/env bash
# My first script
echo "Hello, $USER!"
echo "Today is $(date +%A)."

• The first line, the shebang (#!), tells the system which program should run the file. /usr/bin/env bash finds Bash wherever it's installed.
• Lines starting with # are comments.

Running it

$ chmod +x hello.sh
$ ./hello.sh
Hello, ada!
Today is Tuesday.

• chmod +x makes the file executable (you only do this once).
• ./hello.sh runs it. The ./ means "in the current directory" — Bash doesn't look in the current directory for commands by default, for safety.

You can also run a script without making it executable: bash hello.sh.

A slightly bigger script

#!/usr/bin/env bash
# Create a dated notes file and list the notes folder.

mkdir -p notes
file="notes/$(date +%Y-%m-%d)-meeting.md"
echo "# Meeting notes" > "$file"
echo "Created $file"
ls notes | wc -l

Each time you run it, it creates a file named after today's date. Scripts like this — a few commands you'd otherwise type by hand — are where most automation starts.

Where to keep scripts

Put personal scripts in a folder such as ~/bin or ~/.local/bin, and make sure it's in your PATH (add export PATH="$HOME/.local/bin:$PATH" to ~/.bashrc). Then you can run them from anywhere by name, without ./.

Common mistakes

• Permission denied — the file isn't executable; run chmod +x.
• bad interpreter: /bin/bash^M — the file has Windows line endings (CRLF). Set your editor to use LF line endings, or convert with dos2unix hello.sh.
• command not found when typing hello.sh — use ./hello.sh.