用C/C++程序控制环境变量
In C++, how do i go about using setenv to set the display? I need to set it like this:
export DISPLAY=0.0
1、setenv("DISPLAY",":0.1",1);
If you're calling the xrandr functions from your C++ program, then I would expect setenv() should work for you. The 3rd argument of 1 tells setenv() to overwrite any previous value of argument 1 (DISPLAY). You'd be out of luck if xrandr cached the display name though. In that case, you'd have to re-invoke a program from a shell script: the shell script could set the DISPLAY each time before starting your program. That would be less C++ coding
#include <stdlib.h>
#include <stdio.h>
int main(){
char *env1 = getenv("test11");
printf("test11=%s\n", env1); //show current env variable
setenv("test11","abcd",1); //reset it
env1 = getenv("test11");
printf("test11=%s\n", env1);
//this value reset is gone after the program finished
return 0;
}
g++ setenv.cpp -o mysetenv
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哈哈！有幸在某网站发现这篇文章，读罢，觉得蛮有道理，发来大家一起共勉之
总是被同学们问到，如何学习C和C++才不茫然，才不是乱学，想了一下，这里给出一个总的回复。
' J$ |0 ?! p% w" t5 D6 D: c9 |0 B
一家之言，欢迎拍砖哈。
1、可以考虑先学习C.
/ U$ X+ X/ P; Y ......
1.是不是一个父类写了一个virtual 函数，如果子类覆盖它的函数不加virtual ,也能实现多态?
virtual修饰符会被隐形继承的。private 也被集成，只事派生类没有访问权限而已。virtual可加可不加。子类的空间里有父类的所有变量(static除外)。同一个函数只存在一个实体(inline除外)。子类覆盖它的函数不加virtual ,也能实现多� ......
1.求下面函数的返回值（ 微软）
int func(x)
{
int countx = 0;
while(x)
{
countx ++;
x = x&(x-1);
......
这段源码能在linux下运行！！！ 能识别小数
#include<unistd.h>
#include<stdlib.h>
#include<stdio.h>
#include<string.h>
/*#define NULL 0*/
/* 自定义变量 */
#define&n ......
