strtod()字符串转换成浮点数，strtol()字符串转换成长整型，可指定进制，strtoul()字符串转换成无符号长整型，可指定进制

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本文详细介绍了如何使用 C 语言中的 strtod 和 strtol 函数将字符串转换为浮点数和长整型数字，并展示了不同进制下的转换效果。通过多个实例演示了这些函数的应用场景。

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一、strtod()字符串转换成浮点数，strtol()字符串转换成长整型，可指定进制

测试用例

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

int main()
{
  char str[30] = "20.30300 This is test";
  unsigned char* hexstr="a1b2",*hexstr1 = "0x5F4A8218",hexstr2[] = {'0','x','f','f','3','4','3','a','e','2',0x0d,0x0a,0};
   char *ptr;
   double ret;
   unsigned int iret;

   ret = strtod(str, &ptr);
   printf("数字（double）是 %lf\n", ret);
   printf("字符串部分是 |%s|\n", ptr);

   iret = strtol(str, &ptr,0);    //默认是10进制
   printf("strtol: the num %ld\n", iret);
   printf("remain str: |%s|\n", ptr);

   iret = strtol(str, &ptr,10);  //10进制
   printf("strtol: the num %ld\n", iret);
   printf("remain str: |%s|\n", ptr);

   iret = strtol(str, &ptr,2);  //2进制
   printf("strtol: the num %ld\n", iret);
   printf("remain str: |%s|\n", ptr);

   iret = strtol(str, &ptr,16);  //16进制
   printf("strtol: the num %ld\n", iret);
   printf("remain str: |%s|\n", ptr);

    iret = strtol(str, &ptr,8);  //8进制
   printf("strtol: the num %ld\n", iret);
   printf("remain str: |%s|\n", ptr);

   ///////
   printf("\n\nhexadecimal:\n");
    iret = strtol(hexstr, &ptr,16);  //16进制
   printf("strtol: the num %x\n", iret);
   printf("remain str: |%s|\n", ptr);

   printf("\n\nhexadecimal:\n");
    iret = strtol((const char*)hexstr1, &ptr,16);  //16进制
   printf("strtol: the num %x\n", iret);
   printf("remain str: |%s|\n", ptr);

   printf("\n\nhexadecimal:\n");
    iret = strtoul(hexstr2, &ptr,16);  //16进制,转换成无符号数
   printf("strtol: the num %x\n", iret);
   printf("remain str: |%s|\n", ptr);


   return(0);
}