$ curl -fsSL https://claude.ai/install.sh | head -25
#!/bin/bash

set -e

# Parse command line arguments
TARGET="$1"  # Optional target parameter

# Validate target if provided
if [[ -n "$TARGET" ]] && [[ ! "$TARGET" =~ ^(stable|latest|[0-9]+\.[0-9]+\.[0-9]+(-[^[:space:]]+)?)$ ]]; then
    echo "Usage: $0 [stable|latest|VERSION]" >&2
    exit 1
fi

# Refuse to run under sudo from a regular user's shell. This installer puts
# everything under $HOME, which under sudo typically resolves to root's home:
# the binary lands in /root/.local/bin (or is left root-owned in the user's
# home, depending on the distro's sudo configuration), and the 'claude'
# command is then not found in the user's own shell. Plain root with no sudo
# (containers, CI, root-only systems) is unaffected by this check.
if [ "$(id -u)" -eq 0 ] && [ -n "${SUDO_USER:-}" ] && [ "$SUDO_USER" != "root" ] && [ -z "${CLAUDE_INSTALL_ALLOW_SUDO:-}" ]; then
    echo "Error: do not run this installer with sudo." >&2
    echo "" >&2
    echo "Claude Code installs into your home directory and does not need root access." >&2
    echo "With sudo, the installation would go into root's home directory instead of" >&2
    echo "yours, and the 'claude' command would not work from your own shell." >&2