strtoul,strtol,strtod用于字符串到整形，浮点型的数据的转换

Technorati 标签: strtol, strtoul, strtod

函数原型：

long int strtol ( const char * str, char ** endptr, int base );

unsigned long int strtoul ( const char * str, char ** endptr, int base );

double strtod ( const char * str, char ** endptr );

这几个函数从str指向的字符开始转化，忽略掉前面的空格，遇到错误无法转换的字符则返回，如果endptr不为空，则将该字符存储在endptr里。

对前两个函数，base则表示其进制。

想到之前的一篇笔记：http://www.cppblog.com/izualzhy/archive/2012/07/09/182456.html

需要将”0xE4”转到E4(1个字节)

可以简单的这么写了：

    char str[] = "E4";
    int a;
    a = strtol(str,NULL,16);

看个详细的例子：

/*
 * =====================================================================================
 *       Filename:  strtodata.c
 *    Description:  string to long/unsigned long/double
 *
 *        Version:  1.0
 *        Created:  08/16/2012 07:30:17 PM
 *
 *         Author:  zhy (), [email protected]
 * =====================================================================================
 */

#include <stdio.h>
#include <stdlib.h>

int main()
{
    char numbers[] = "2001 60c0c0 -1101110100110100100000 0x6fffff";
    char *pEnd;
    long int li1,li2,li3,li4;
    li1 = strtol(numbers, &pEnd, 10);
    li2 = strtol(pEnd, &pEnd, 16);
    li3 = strtol(pEnd, &pEnd, 2);
    li4 = strtol(pEnd, NULL, 0);
    printf("The decimal equivalents are: %ld, %ld, %ld, %ld.\n",li1,li2,li3,li4);

    char digits[] = "365.24   29.53 -1.23456";    
    double d1,d2,d3;
    d1 = strtod(digits, &pEnd);
    printf("%c\n", *pEnd);
    d2 = strtod(pEnd, &pEnd);
    d3 = strtod(pEnd, NULL);
    printf("The moon completes %f/%f orbits per Earth yes.%f\n",d1,d2,d3);

    return 0;
}

运行结果：

The decimal equivalents are: 2001, 6340800, -3624224, 7340031.
 
The moon completes 365.240000/29.530000 orbits per Earth yes.-1.234560

参考资料：

http://www.cplusplus.com/reference/clibrary/cstdlib/strtoul/