User Input & Arguments

Scripts rarely run with everything hardcoded — they take input either interactively while running, or as arguments typed right after the script's name.

Reading input while the script runs

read pauses the script and waits for the person running it to type something and press Enter:

bash ask.sh

#!/bin/bash
read -p "What's your name? " name
echo "Nice to meet you, $name."

Terminal output

What's your name? Priya
Nice to meet you, Priya.

-p lets you show a prompt on the same line, instead of needing a separate echo before the read.

Command-line arguments

Arguments typed after a script's name are available inside it as $1, $2, and so on. $0 is the script's own name, and $# is the number of arguments given:

$ terminal

./greet.sh Priya Developer

bash greet.sh

#!/bin/bash
echo "Script name: $0"
echo "First arg: $1"
echo "Second arg: $2"
echo "Total args: $#"

Terminal output

Script name: ./greet.sh
First arg: Priya
Second arg: Developer
Total args: 2

"$@" vs "$*"

Both represent "all the arguments," but they behave differently once you loop over them:

bash loop-args.sh

#!/bin/bash
# called as: ./loop-args.sh "New York" Paris
for arg in "$@"; do
    echo "Arg: $arg"
done

Terminal output

Arg: New York
Arg: Paris

Note: "$@" (quoted) expands each argument as its own separate word, so "New York" stays together as one item. "$*" (quoted) instead joins everything into a single string. Almost always, "$@" is what you want when looping over arguments — it's the one that survives arguments containing spaces correctly.

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