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Common Helper Scripts

This directory contains common helper scripts that can be shared across multiple features to avoid code duplication.

common-setup.sh

A helper script that provides common setup functions used across multiple features.

Functions

determine_user_from_input

Determines the appropriate non-root user based on the input username.

Usage:

# Source the helper script
source "${SCRIPT_DIR}/_lib/common-setup.sh"

# Determine the user
USERNAME=$(determine_user_from_input "${USERNAME}" "root")

Parameters:

  • $1 (required): Input username from feature configuration (e.g., "automatic", "auto", "none", or a specific username)
  • $2 (optional): Fallback username when no user is found in automatic mode (defaults to "root")

Behavior:

  • "auto" or "automatic":

    • First checks if _REMOTE_USER environment variable is set and is not "root"
    • If _REMOTE_USER is root or not set, searches for an existing user from the priority list:
      1. devcontainer
      2. vscode
      3. node
      4. codespace
      5. User with UID 1000 (from /etc/passwd)
    • If no user is found, returns the fallback user (default: "root")

  • "none": Always returns "root"

  • Specific username:

    • Validates the user exists using id -u
    • If the user exists, returns that username
    • If the user doesn't exist, returns "root"

Examples:

# Basic usage with default fallback (root)
USERNAME=$(determine_user_from_input "automatic")

# With custom fallback
USERNAME=$(determine_user_from_input "automatic" "vscode")

# Explicit user
USERNAME=$(determine_user_from_input "myuser")

# None (always returns root)
USERNAME=$(determine_user_from_input "none")

Return Value: Prints the resolved username to stdout, which can be captured using command substitution.

Testing

Tests for the helper scripts are located in /test/.common/. Run the tests with:

bash test/.common/test-common-setup.sh

Edge Cases

The helper handles several edge cases:

  1. Missing awk: Some systems (like Mariner) don't have awk by default. Features should install it before sourcing the helper if needed.

  2. UID 1000 lookup: The user with UID 1000 is included in the search as it's commonly the first non-system user created.

  3. _REMOTE_USER behavior: When _REMOTE_USER is set to a non-root user, it takes priority over all other detection methods in automatic mode.

  4. Empty user list entries: The helper safely handles empty entries in the user detection loop.

Migration Guide

To migrate an existing feature to use the common helper:

Before:

# Determine the appropriate non-root user
if [ "${USERNAME}" = "auto" ] || [ "${USERNAME}" = "automatic" ]; then
    USERNAME=""
    POSSIBLE_USERS=("vscode" "node" "codespace" "$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd)")
    for CURRENT_USER in "${POSSIBLE_USERS[@]}"; do
        if id -u ${CURRENT_USER} > /dev/null 2>&1; then
            USERNAME=${CURRENT_USER}
            break
        fi
    done
    if [ "${USERNAME}" = "" ]; then
        USERNAME=root
    fi
elif [ "${USERNAME}" = "none" ] || ! id -u ${USERNAME} > /dev/null 2>&1; then
    USERNAME=root
fi

After:

# Source common helper functions
SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
source "${SCRIPT_DIR}/_lib/common-setup.sh"

# Determine the appropriate non-root user
USERNAME=$(determine_user_from_input "${USERNAME}" "root")

Note: For features like common-utils that create users and need a different fallback, use:

USERNAME=$(determine_user_from_input "${USERNAME}" "vscode")