import type { Command } from '@oclif/core';
/**
 * Output data as JSON or plain text based on the json flag.
 * @param command The command instance (for this.log)
 * @param json Whether to output as JSON
 * @param data The data to output (for JSON mode)
 * @param plainFn Function to call for plain text output
 */
export declare function outputJsonOrPlain<T>(command: Command, json: boolean, data: T, plainFn: () => void): void;
/**
 * Truncate a string to a maximum length, adding ellipsis if truncated.
 */
export declare function truncate(str: string, maxLen: number): string;
/**
 * Create a horizontal separator line.
 */
export declare function tableSeparator(width: number, char?: string): string;
/**
 * Format a line number with consistent width padding.
 */
export declare function formatLineNumber(line: number, width?: number): string;
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