c-缺少最后一个IP地址

Question

我有一个文件，正在尝试将ip地址存储到一个数组中。我的计划是将数据存储到逗号，或者将地址后面的字符存储到伪变量中。由于某种原因，我的代码一直工作到第2行。任何帮助都会很棒。

Blacklist.csv：

46.30.45.65, good.recycle2learn.com
22.51.66.23, hothouse.com
83.98.11.48, monkeyhouse.com

代码：

void Blacklist()
{
  FILE *blist;
  char quotations = 0;
  blist = fopen("blacklist.csv", "r");
  if (blist == NULL)
  {
    //Quit if something goes wrong
    exit(EXIT_FAILURE);
  }
  for (int i = 0; i <= 3; i++)
  {
    fscanf(blist, "%d.%d.%d.%d,", &blacklist[i][0], &blacklist[i][1],
        &blacklist[i][2], &blacklist[i][3]);
    while (quotations != 'n')
    {
      fscanf(blist, "%c,", &quotations);
    }
  }
  for (int i = 0; i <= 3; i++)
  {
    printf("%d.%d.%d.%dn", blacklist[i][0], blacklist[i][1], blacklist[i][2],
        blacklist[i][3]);
  }
}

Answer 1

读取每一行后，您不会重置quotations变量（考虑到它的用途，它的名称不太好）。一旦到达第一个换行符，就再也不会进入while循环。如果您在调试器中运行代码，您就会看到这种情况的发生。

读取ip地址后重置变量：

for (int i = 0; i < 3; i++) // <-- use < instead of <=
{
    fscanf(blist, "%d.%d.%d.%d,", &blacklist[i][0], &blacklist[i][1], &blacklist[i][2], &blacklist[i][3]);
    quotations = 0; // <-- add this
    while (quotations != 'n')
    {
        fscanf(blist, "%c", &quotations); // <-- no comma after %c
    }
}

或者使用do..while循环：

for (int i = 0; i < 3; i++)
{
    fscanf(blist, "%d.%d.%d.%d,", &blacklist[i][0], &blacklist[i][1], &blacklist[i][2], &blacklist[i][3]);
    do
    {
        fscanf(blist, "%c", &quotations);
    }
    while (quotations != 'n');
}

更新：也就是说，您的代码没有处理csv文件在每个IP条目之间包含空行（如您的问题所示）或在最后一个条目之后缺少换行符的可能性。为了解决这些问题，请尝试使用fgets()或getline()将文件逐行读取到本地缓冲区中，并根据需要使用sscanf()解析缓冲区。

int blacklist[3][4];
int numblacklist;
void Blacklist()
{
  FILE *blist;
  char line[64];
  memset(blacklist, 0, sizeof(blacklist));
  numblacklist = 0;
  blist = fopen("blacklist.csv", "r");
  if (blist == NULL)
  {
    //Quit if something goes wrong
    exit(EXIT_FAILURE);
  }
  while (fgets(line, 64, blist))
  {
    if (sscanf(line, "%d.%d.%d.%d,", &blacklist[numblacklist][0], &blacklist[numblacklist][1], &blacklist[numblacklist][2], &blacklist[numblacklist][3]) == 4)
    {
      numblacklist++;
      if (numblacklist == 3)
        break;
    }
  }
  fclose(blist);
  for (int i = 0; i < numblacklist; i++)
  {
    printf("%d.%d.%d.%dn", blacklist[i][0], blacklist[i][1], blacklist[i][2], blacklist[i][3]);
  }
}

或者：

int blacklist[3][4];
int numblacklist;
void Blacklist()
{
  FILE *blist;
  size_t linelen;
  char *line;
  memset(blacklist, 0, sizeof(blacklist));
  numblacklist = 0;
  blist = fopen("blacklist.csv", "r");
  if (blist == NULL)
  {
    //Quit if something goes wrong
    exit(EXIT_FAILURE);
  }
  line = NULL;
  linelen = 0;
  while (getline(&line, &linelen, blist) != -1)
  {
    if (sscanf(line, "%d.%d.%d.%d,", &blacklist[numblacklist][0], &blacklist[numblacklist][1], &blacklist[numblacklist][2], &blacklist[numblacklist][3]) == 4)
    {
      numblacklist++;
      if (numblacklist == 3)
        break;
    }
  }
  free(line);
  fclose(blist);
  for (int i = 0; i < numblacklist; i++)
  {
    printf("%d.%d.%d.%dn", blacklist[i][0], blacklist[i][1], blacklist[i][2], blacklist[i][3]);
  }
}