读书共享 Primer Plus C-part 4

  第四章 字符串和格式化输入输出

• 关于printf

-  左对齐

 

#include<stdio.h>

void main()
{
  char str [100] = "liuchuanwu";
  printf("%20s
",str);
  printf("%-20s
",str);



}

　　

• 关于浮点数的打印

       

#include<stdio.h>
#include<string.h>
int main()
{
  char str [100] = "liuchuanwu";
  short s1 = 1111;
  short s2 =1;
  int   i1= 1111111111;
  long int l1= 1111111111111111111;
  long int l2=11;
  float f1 = 1234.6789;
  printf("%d  %d
",sizeof(s1), s1);
  printf("%d  %d
",sizeof(s2), s2);
  printf("%d  %d
",sizeof(i1), i1);
  printf("%d  %ld
",sizeof(l1), l1);
  printf("%d  %ld
",sizeof(l2), l2);
  printf("%20s
",str);
  printf("%-20s
",str);
  printf("%d 
  %d
",sizeof(str),strlen(str));


  printf("%2.3f 
",f1);
  printf("%0.3f 
",f1);
  printf("%-10.3f 
",f1);
  printf("%10.3f 
",f1);
  return 0;


}

    %x.y x小于浮点数本身的大小全部打印 x大于浮点数本身按照x长度打印。

     x的长度 指整数长度+小数长度+1

       

•  关于字符串打印长度

    

#include<stdio.h>
#include<string.h>
int main()
{
  char str [100] = "liuchuanwu";
  printf("%20.1s 
",str);
  return 0;


}

  对于%20.1s 20指的是整个打印占多大，.1指的是打印多少个真正的字符。

       

• 对于长字符串处理

     

#include<stdio.h>
#include<string.h>
int main()
{
  char str [100] = "liuchuanwu";
  printf("%20.1s 
",str);
  printf("liuchuanwu is a handman
");
  printf("liuchuanwu is a 
handman
");
  printf("liuchuanwu is a "
          "handman
");


  return 0;


}

      

•  关于sizeof 和strlen

     

#include<stdio.h>
#include<string.h>
int main()
{
  char str [100] = "liuchuanwu";
  printf("%20s
",str);
  printf("%-20s
",str);
  printf("%d 
  %d
",sizeof(str),strlen(str));
  return 0;


}

　　sizeof 所占字节大小 strlen到还有多久

      

•  关于scanf

         scanf 的第二个输入参数是指针，所以针对基本类型需要使用&获取内存地址，对于字符串则不需要，字符串本身为指针。

       

#include<stdio.h>
#include<string.h>
int main()
{
  char str [100] = "liuchuanwu";
  int age = 0;
  printf("input your name and age 
",str);
  scanf("%s",str);
  scanf("%d",&age);
  printf("%d 
%s
",age,str);

  return 0;


}

        

     残留问题针对空行如何处理