#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(int argc, char *argv[])
{
    FILE *in, *out;
    int ch;
    char name[LEN];
    int count = 0;
    if (argc < 2)
    {
        fprintf(stderr, "usage:%s filename \n", argv[0]);
        exit(EXIT_FAILURE);
        }
    if ((in = fopen(argv[1], "r")) == NULL)
    {
        fprintf(stderr, "i couldn't open the file \"%s\"\n", argv[1]);
        exit(EXIT_FAILURE);
            }
    strncpy(name, argv[1], LEN - 5);
    name[LEN - 5] = '\0';
    strcat(name, ".red");
    if ((out = fopen(name, "w")) == NULL)
    {
        fprintf(stderr, "can't create output file .\n");
        exit(3);
            }
    while ((ch = getc(in)) != EOF)
        if (count++ % 3 == 0)
            putc(ch, out);
    if (fclose(in) != 0 | fclose(out) != 0)
        fprintf(stderr, "Error in closing files \n");
    return 0;

}

程序多处看不懂，麻烦详细解释下。程序中 main (int argc ,char *argv []）不懂，文件操作更是没有看明白。程序运行也不成功

谢谢

是什么原因？这个是书上的习题，学习C语言文件操作，就一直被卡在这了