strtok,strtok_r,strsep--extract tokens from strings
Tje strsep() function was introduced as a replacement for strtok, since the latter cannot handle empty fileds. However, strtok conforms to C89/C99 and hence is more portable.
#include <string.h>
char *strtok(char *str, const char *delim);
char *strtok_r(char *str, const char *delim, char **saveptr); 可重入
char *strsep(char **stringp, const char *delim);
根据delim字符串分解str。
saveptr用于保存每次调用完参数后下一次进行字符串分割时的起始地址,内部设定。
delim可为多个字符,每个字符都分解str,str中出现的不连续分解字符都改写为‘