std::getenv
Defined in header <cstdlib> | ? | ? |
|---|---|---|
char* getenv( const char* env_var ); | ? | ? |
搜索环境清单主机环境%28提供OS%29，用于与env_var并返回指向与匹配的环境列表成员关联的C字符串的指针。
This function is not required to be thread-safe. Another call to getenv, as well as a call to the POSIX functions setenv(), unsetenv(), and putenv() may invalidate the pointer returned by a previous call or modify the string obtained from a previous call. | (until C++11) |
|---|---|
This function is thread-safe (calling it from multiple threads does not introduce a data race) as long as no other function modifies the host environment. In particular, the POSIX functions setenv(), unsetenv(), and putenv() would introduce a data race if called without synchronization. | (since C++11) |
修改由getenv调用未定义的行为。
参数
env_var | - | null-terminated character string identifying the name of the environmental variable to look for |
|---|
返回值
字符串标识环境变量的值，如果找不到该变量，则为空指针。
注记
关于POSIX系统，环境变量也可以通过全局变量访问。environ，宣布为extern char **environ;在<unistd.h>，通过第三个可选的论点，envp...的主要功能...
例
二次
#include <iostream>
#include <cstdlib>
int main()
{
if(const char* env_p = std::getenv("PATH"))
std::cout << "Your PATH is: " << env_p << '\n';
}二次
可能的产出：
二次
Your PATH is: /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games二次
另见
c getenv文件
*。
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