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\n",str);
  printf("%-20s\n",str);
 
}

　　

• 关于浮点数的打印

#include<stdio.h>
#include<string.h>
int main()
{
  char str [] = "liuchuanwu";
  short s1 = ;
  short s2 =;
  int   i1= ;
  long int l1= ;
  long int l2=;
  float f1 = 1234.6789;
  printf("%d  %d\n",sizeof(s1), s1);
  printf("%d  %d\n",sizeof(s2), s2);
  printf("%d  %d\n",sizeof(i1), i1);
  printf("%d  %ld\n",sizeof(l1), l1);
  printf("%d  %ld\n",sizeof(l2), l2);
  printf("%20s\n",str);
  printf("%-20s\n",str);
  printf("%d \n  %d\n",sizeof(str),strlen(str));
 
  printf("%2.3f \n",f1);
  printf("%0.3f \n",f1);
  printf("%-10.3f \n",f1);
  printf("%10.3f \n",f1);
  return ;
 
}

%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 [] = "liuchuanwu";
  printf("%20.1s \n",str);
  return ;
 
}

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 [] = "liuchuanwu";
  printf("%20.1s \n",str);
  printf("liuchuanwu is a handman\n");
  printf("liuchuanwu is a \
handman\n");
  printf("liuchuanwu is a "
          "handman\n");
 
  return ;
 
}

• 关于sizeof 和strlen

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

　　sizeof 所占字节大小 strlen到\0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 [] = "liuchuanwu";
  int age = ;
  printf("input your name and age \n",str);
  scanf("%s",str);
  scanf("%d",&age);
  printf("%d \n%s\n",age,str);
 
  return ;
 
}

残留问题针对空行如何处理