C编程-如何将输出图片文件设置为.pgm格式？

Question

Instead of asking user to enter output name I need the program to automatically create it as out1.pgm. How can do I it?

       {
        printf("Enter image filename: ");
        scanf("%s", fileName);

        img = readpic(fileName);

        printf("Successfully read image file '%s'\n", fileName);
        printf("Adjust brightness: ");
        scanf("%d", &brightness);

        option1(img, brightness);

        printf("Enter image filename for output: ");
        scanf("%s", fileName);

        writeoutpic(fileName,img);



        free(img);
        img = NULL;
        return(EXIT_SUCCESS);
    }

Answer 1

Change scanf("%s", fileName); to strcpy(fileName, "out1.pgm");