trim的实现

void ltrim(char *s)
{
 char *p;
 p = s;
 while(*p == ' ' || *p == '\t'){*p++;}
 strcpy(s,p);
}

void rtrim(char *s)
{
 int i;

 i = strlen(s)-1;
 while((s[i] == ' ' || s[i] == '\t') && i >= 0){i--;};
 s[i+1] = '\0';
}

void trim(char *s){
    ltrim(s);
    rtrim(s);
}