Grep MCP Server

Instructions

Implementation Reference

• src/index.ts:534-579 (handler)

  The async handler function for the 'grep_advanced' tool. Validates input args against dangerous flags and executes the grep command via executeGrep helper, returning results or errors.

  async ({ args }) => {
    // Basic validation to prevent potentially dangerous operations
    const dangerousFlags = [
      '--devices=', // Device operations could be dangerous
      '--binary-files=', // Binary file operations
      '-f', '--file', // Reading patterns from files
      '-D', '--devices', // Device handling
    ];
    
    const hasUnsafeFlag = args.some(arg => 
      dangerousFlags.some(dangerous => arg.startsWith(dangerous))
    );
    
    if (hasUnsafeFlag) {
      return {
        content: [
          {
            type: "text",
            text: `Error: This command contains potentially unsafe flags. Please use the specific grep tools for safety.`,
          },
        ],
      };
    }
    
    try {
      const result = await executeGrep(['grep', ...args]);
      
      return {
        content: [
          {
            type: "text",
            text: `Exit Code: ${result.exitCode}\n\nResults:\n${result.stdout}${result.stderr ? `\n\nErrors:\n${result.stderr}` : ''}`,
          },
        ],
      };
    } catch (error) {
      return {
        content: [
          {
            type: "text",
            text: `Error executing grep: ${error instanceof Error ? error.message : String(error)}`,
          },
        ],
      };
    }
  }

• src/index.ts:531-533 (schema)

  Zod input schema for the 'grep_advanced' tool, defining a single parameter 'args' as an array of strings.

  {
    args: z.array(z.string()).describe("Array of grep arguments (excluding 'grep' itself)"),
  },

• src/index.ts:528-580 (registration)

  Registration of the 'grep_advanced' MCP tool using server.tool, including name, description, schema, and inline handler.

  server.tool(
    "grep_advanced",
    "Execute grep with custom arguments (advanced usage)",
    {
      args: z.array(z.string()).describe("Array of grep arguments (excluding 'grep' itself)"),
    },
    async ({ args }) => {
      // Basic validation to prevent potentially dangerous operations
      const dangerousFlags = [
        '--devices=', // Device operations could be dangerous
        '--binary-files=', // Binary file operations
        '-f', '--file', // Reading patterns from files
        '-D', '--devices', // Device handling
      ];
      
      const hasUnsafeFlag = args.some(arg => 
        dangerousFlags.some(dangerous => arg.startsWith(dangerous))
      );
      
      if (hasUnsafeFlag) {
        return {
          content: [
            {
              type: "text",
              text: `Error: This command contains potentially unsafe flags. Please use the specific grep tools for safety.`,
            },
          ],
        };
      }
      
      try {
        const result = await executeGrep(['grep', ...args]);
        
        return {
          content: [
            {
              type: "text",
              text: `Exit Code: ${result.exitCode}\n\nResults:\n${result.stdout}${result.stderr ? `\n\nErrors:\n${result.stderr}` : ''}`,
            },
          ],
        };
      } catch (error) {
        return {
          content: [
            {
              type: "text",
              text: `Error executing grep: ${error instanceof Error ? error.message : String(error)}`,
            },
          ],
        };
      }
    }
  );

• src/index.ts:21-60 (helper)

  Shared helper function to safely spawn and execute grep processes, capturing stdout, stderr, and exit code. Used by 'grep_advanced' and other grep tools.

  async function executeGrep(args: string[]): Promise<{ stdout: string; stderr: string; exitCode: number }> {
    return new Promise((resolve) => {
      // Ensure we're only calling grep with safe arguments
      if (!args.includes('grep')) {
        args.unshift('grep');
      }
      
      const child = spawn('grep', args.slice(1), {
        stdio: ['pipe', 'pipe', 'pipe'],
        shell: false,
      });
  
      let stdout = '';
      let stderr = '';
  
      child.stdout.on('data', (data) => {
        stdout += data.toString();
      });
  
      child.stderr.on('data', (data) => {
        stderr += data.toString();
      });
  
      child.on('close', (code) => {
        resolve({
          stdout,
          stderr,
          exitCode: code || 0,
        });
      });
  
      child.on('error', (error) => {
        resolve({
          stdout: '',
          stderr: error.message,
          exitCode: 1,
        });
      });
    });
  }