freeCodeCamp/guide/chinese/c/short-circuit-evaluation/index.md

title	localeTitle
Short-Circuit Evaluation	短路评估

短路评估

仅当第一个参数不足以确定表达式的值时，短路评估才包括检查或执行第二个参数。

您可以使用&&和||进行短路评估运营商。

&&运算符的示例：

  canOpenFile(filename) && openFile(filename); // If you can open the file then open it. 

上面的例子相当于：

  if ( canOpenFile(filename) ) { 
    openFile(filename); 
  } 

示例包含||运营商：

  isServerOn || startServer(); // If the server is not on then start it. 

The example above is equivalent to:

 if ( !isServerOn ) { 
   startServer(); 
 } 

Keep it all together in real example

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

char *getName(); 

int main(int argc, char *argv[]) { 
   // Get first argument passed via terminal 
   char *name = argv[1]; 

   // If name is not passed via terminal then print message and then get the name 
   name || printf("Please give me your name:") && (name = getName()); 

   printf("Hello %s\n", name); 
} 

char *getName() { 
   // Allocate memory 
   char *name = malloc(30); 

   scanf("%s", name); 
   return name; 
}