C語言實現去除字符串首尾空格

/*
C語言去除字符串首尾空格，trim()函數實現
https://blog.csdn.net/u013022032/article/details/50521465
*/ 
#include <stdio.h> 
#include <stdlib.h> 
#include <string.h> 
#include <ctype.h> 

//去除尾部空白字符 包括\t \n \r  
/*
標准的空白字符包括：
' '     (0x20)    space (SPC) 空格符
'\t'    (0x09)    horizontal tab (TAB) 水平制表符    
'\n'    (0x0a)    newline (LF) 換行符
'\v'    (0x0b)    vertical tab (VT) 垂直制表符
'\f'    (0x0c)    feed (FF) 換頁符
'\r'    (0x0d)    carriage return (CR) 回車符
//windows \r\n linux \n mac \r
*/ 
char *rtrim(char *str) 
{ 
    if (str == NULL || *str == '\0') 
    { 
        return str; 
    } 
    int len = strlen(str); 
    char *p = str + len - 1; 
    while (p >= str && isspace(*p)) 
    { 
        *p = '\0'; --p; 
    } 
    return str; 
} 


//去除首部空格 
char *ltrim(char *str) 
{ 
    if (str == NULL || *str == '\0') 
    { 
        return str; 
    } 
    int len = 0; 
    char *p = str;
    while (*p != '\0' && isspace(*p)) 
    { 
        ++p; ++len; 
    } 
    memmove(str, p, strlen(str) - len + 1); 
    return str; 
} 


//去除首尾空格 

char *trim(char *str) 
{ 
    str = rtrim(str); 
    str = ltrim(str); 
    return str; 
} 

void demo() 
{ 
    char str[] = "   ab  c \r \n \t";
    printf("before trim:%s\n", str); 
    char *p = trim(str); 
    printf("after trim:%s\n", p); 
} 

int main(int argc, char **argv) 
{ 
    demo(); 
    return 0; 
}