/** True for `"1"` or `"true"` (any case). */
export declare const isTruthyEnv: (value?: string) => boolean;
export declare const DEFAULT_ENV_FILE = ".env";
export declare const PROJECT_ENV_FILES: readonly [".env", ".env.local"];
/** Parse a dotenv-style file into key/value pairs (no `$VAR` expansion). */
export declare function parseEnvFile(filePath: string): Record<string, string>;
/**
 * Merge env files (later files win) and keep only allowlisted keys with
 * non-empty values. Values are never logged by this helper.
 */
export declare function loadAllowlistedEnvFiles(filePaths: string[], allowlist: readonly string[]): Record<string, string>;
/** Load allowlisted keys from the usual project env files (`.env`, `.env.local`). */
export declare function loadAllowlistedProjectEnv(projectDir: string, allowlist: readonly string[], fileNames?: readonly string[]): Record<string, string>;
/** POSIX-style env names: letters, digits, underscores; must not start with a digit. */
export declare function assertValidEnvVarName(name: string, flag?: string): void;
/**
 * Create or update `name=value` in an env file. Replaces the first matching
 * assignment (including a commented one) and otherwise appends.
 */
export declare function upsertEnvVar(filePath: string, name: string, value: string): void;
/** Remove every assignment for `name`, including a commented one. */
export declare function removeEnvVar(filePath: string, name: string): void;
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