strtok 表现出不良行为

Question

以下是我的代码片段：

int main()
{
   char *str[4];
   char *ptr;

   char Str[25];
   char Str1[25];
   memset(Str,32,25);
   char temp[25];
   sprintf(Str,"123;;False;CXL;;true");
   printf("Old String [%s]",Str);
   ptr = &Str ;
   str[0]=strtok(ptr,";");
   str[1]=strtok(NULL,";");
   str[2]=strtok(NULL,";");
   str[3]=strtok(NULL,";");

   printf("str[0] =[%s]",str[0]);
   printf("str[1] =[%s]",str[1]);
   printf("str[2] =[%s]",str[2]);
   printf("str[3] =[%s]",str[3]);

   //strncpy(temp,str,25);
   memcpy(str[0],"345",3);
   sprintf(Str1,"%s;%s;%s;%s",str[0],str[1],str[2],str[3]);
   printf("New String [%s]",Str1);
   return 0;
}

我担心的是为什么它会忽略原始字符串中的 'null' 值？根据输出，我得到 4 个标记，但实际上我有 6 个带分隔符 ';' 的标记，它忽略了 b/w 中的 'null' 值，并且不将它们视为单独的标记。

输出为：

Old String [123;;False;CXL;;true]
str[0] =[123]str[1] =[False]str[2] =[CXL]str[3] =[true]
New String [345;False;CXL;true]

是否有我不知道的解决方法？

谢谢！

Answer 1

strsep MAN 说

The strsep() function is intended as a replacement for the strtok() function. While the strtok() function should be preferred for portability reasons (it conforms to ISO/IEC 9899:1990 ("ISO C90")) it is unable to handle empty fields, i.e., detect fields delimited by two adjacent delimiter characters, or to be used for more than a single string at a time. The strsep() function first appeared in 4.4BSD.

例子

char *t, *str, *save;

save = str = strdup("123;;False;CXL;;true");
while ((t = strsep(&str, ";")) != NULL)
    printf("Token=%s\n", t);

free(save);

输出

Token=123
Token=
Token=False
Token=CXL
Token=
Token=true

strtok 表现出不良行为

strtok showing undesirable behaviour

c

string

pointers

tokenize