在 C 中复制字母数字字符

Question

我有一个 char 文本数组，想将字母数字小写值存储在指针数组中。即 mystr 应该指向“50sometexthere”的 char[]

char[] myline = " 50 Some Text  Here ";
char *mystr = (char *)malloc(128 * sizeof(char));

char *tmp = myline;

while (*tmp != '\0'){
 if (isalnum(*tmp))
  strcat(mystr,(char*) tolower(*tmp));
 tmp++;
}

我做错了什么？

Answer 1

char *myline = " 50 Some Text  Here ";
char *mystr = (char *)malloc(128); //sizeof char is always 1

char *tmp = myline;
char *tmpdest = mystr;

while (*tmp != '\0'){
 if (isalnum(*tmp))
  *tmpdest++ = tolower(*tmp); //this line is changed!
 tmp++;
}

*tmpdest = '\0';

HTH