c - C语言：使用strtok()一次后如何获取剩余字符串

Question

我的字符串是 "A,B,C,D,E"
分隔符是 ","
执行 strtok() 一次后如何得到剩余的字符串，即 "B,C,D,E"

char a[] = "A,B,C,D,E";
char * separator = ",";
char * b = strtok(a,separator);
printf("a: %s\n", a);
printf("b: %s\n", b);

输出为：
a: A
b: A

但是如何得到结果
a: B,C,D,E
b: A

谢谢。

Answer 1

您可以更改分隔符集，因此只需传递一个空字符串：

char a[] = "A,B,C,D,E";
char * separator = ",";
char * b = strtok(a, separator);
printf("b: %s\n", b);
char * c = strtok(NULL, "");
printf("c: %s\n", c);

Answer 2

不要strtok()用于这个，因为那不是它的用途。

用于strchr()查找第一个分隔符，然后从那里开始：

char a[] = "A,B,C,D,E";
const char separator = ',';
char * const sep_at = strchr(a, separator);
if(sep_at != NULL)
{
  *sep_at = '\0'; /* overwrite first separator, creating two strings. */
  printf("first part: '%s'\nsecond part: '%s'\n", a, sep_at + 1);
}

Answer 3

strtok记住它使用的最后一个字符串以及它的结束位置。要获取下一个字符串，请使用NULL第一个参数再次调用它。

char a[] = "A,B,C,D,E";
const char *separator = ",";
char *b = strtok(a, separator);
while (b) {
    printf("element: %s\n", b);
    b = strtok(NULL, separator);
}

注意：这不是线程安全的。

Answer 4

尝试这个：

char a[] = "A,B,C,D,E";
char * end_of_a = a + strlen(a); /* Memorise the end of s. */
char * separator = ",";
char * b = strtok(a, separator);
printf("a: %s\n", a);
printf("b: %s\n", b);

/* There might be some more tokenising here, assigning its result to b. */

if (NULL != b)
{
  b = strtok(NULL, separator);
}

if (NULL != b)
{ /* Get reference to and print remainder: */
  char * end_of_b = b + strlen(b);

  if (end_of_b != end_of_a) /* Test whether there really needs to be something, 
                        will say tokenising did not already reached the end of a, 
                        which however is not the case for this example.  */
  {
    char * remainder = end_of_b + 1;
    printf("remainder: `%s`\n", remainder);
  }   
}

Answer 5

如果 usingstrtok不是必需的，则可以使用strchr，因为分隔符是单个字符：

char a[] = "A,B,C,D,E";
char *sep = strchr(a, ',');
*sep = '\0';
puts(a);
puts(sep + 1);

Answer 6

printf("a: %s\n", a+1+strlen(b));

尝试这个

Answer 7

有更好的方法来处理 ip 地址，但这是一个实际示例，需要在执行期间的某个时间点将分隔符从 更改'.'为'/'.

struct Ip split_ip_by_octet(char ip_string[]) {

    struct Ip ip;
    char * value_before_delimeter = strtok(ip_string, "."); // N. 

    if (value_before_delimeter != NULL) {
        sscanf(value_before_delimeter, "%d", &ip.octet_1);
        value_before_delimeter = strtok(NULL, ".");        // n.N.

        sscanf(value_before_delimeter, "%d", &ip.octet_2);
        value_before_delimeter = strtok(NULL, ".");        // n.n.N.n/n

        sscanf(value_before_delimeter, "%d", &ip.octet_3);
        value_before_delimeter = strtok(NULL, "/");        // n.n.n.N/n

        sscanf(value_before_delimeter, "%d", &ip.octet_4);
        value_before_delimeter = strtok(NULL, "");         // n.n.n.n/N

        sscanf(value_before_delimeter, "%d", &ip.mask);
    }
    return ip; 
}