Positional Parameters & Special Variables

$0, $1, $#, $@, and the exit status code $?

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Scripts accept command-line arguments accessible via positional parameters ($1, $2), while special variables inspect exit codes and process counts.

Key Special Variables

$0: The script filename or path.

$1, $2 ... $9: Positional arguments passed to the script (use ${10} for two digits).

$#: The total count of arguments passed.

$@: All arguments as a separate list of words.

$?: The EXIT STATUS CODE of the last executed command (0 = Success; non-zero = Failure).

Inspecting Arguments and Exit Status

Try It Yourself »

#!/usr/bin/env bash

if [ "$#" -lt 1 ]; then
    echo "Usage: $0 <target_directory>"
    exit 1
fi

TARGET_DIR="$1"
echo "Creating backup for: $TARGET_DIR"
mkdir -p "$TARGET_DIR"

# Check exit code of previous mkdir command
if [ "$?" -eq 0 ]; then
    echo "Directory created successfully!"
fi

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Test Yourself With Exercise

+15 XP

Which special variable in Bash holds the exit status code of the most recently executed command?

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