Function cmd_tail

components/finsh/msh_file.c:741–841

MSH_CMD_EXPORT_ALIAS(cmd_echo, echo, echo string to file);

static int cmd_tail(int argc, char **argv)
{
    int fd;
    char c = RT_NULL;
    char *file_name = RT_NULL;
    rt_uint32_t total_lines = 0;
    rt_uint32_t target_line = 0;
    rt_uint32_t current_line = 0;
    rt_uint32_t required_lines = 0;
    rt_uint32_t start_line = 0;

    if (argc < 2)
    {
        rt_kprintf("Usage: tail [-n numbers] <filename>\n");
        return -1;
    }
    else if (argc == 2)
    {
        required_lines = 10; /* default: 10 lines from tail */
        file_name = argv[1];
    }
    else if (rt_strcmp(argv[1], "-n") == 0)
    {
        if (argv[2][0] != '+')
        {
            required_lines = atoi(argv[2]);
        }
        else
        {
            start_line = atoi(&argv[2][1]); /* eg: +100, to get the 100 */
        }
        file_name = argv[3];
    }
    else
    {
        rt_kprintf("Usage: tail [-n numbers] <filename>\n");
        return -1;
    }

    fd = open(file_name, O_RDONLY);
    if (fd < 0)
    {
        rt_kprintf("File doesn't exist\n");
        return -1;
    }

    while ((read(fd, &c, sizeof(char))) > 0)
    {
        if(total_lines == 0)
        {
            total_lines++;
        }
        if (c == '\n')
        {
            total_lines++;
        }
    }