c语言getenv函数_getenv（）函数与C ++中的示例

c语言getenv函数

C ++ getenv()函数 (C++ getenv() function)

getenv() function is a library function of cstdlib header. It is used to get the environment string. It accepts a parameter which is an environment variable name (platform dependent, it may either case sensitive or not) and returns a C-string that contains the value of the environment variable specified as the parameter.

getenv()函数是cstdlib标头的库函数。它用于获取环境字符串。它接受作为环境变量名称的参数(取决于平台，可能区分大小写)，并返回一个C字符串，其中包含指定为参数的环境变量的值。

Note: The function is the platform-dependent if specified parameter (environment variable) is not defined, it returns a null pointer.

注意：如果未定义指定的参数(环境变量)，则该函数与平台有关，它将返回空指针。

Syntax of getenv() function:

getenv()函数的语法：

C++11:

C ++ 11：

    char* getenv (const char* name);

Parameter(s):

参数：

name – represents the name of the environment variable.
name –代表环境变量的名称。

Return value:

返回值：

The return type of this function is char*, it returns a C-string that contains the value of the environment variable specified as parameter.

该函数的返回类型为char * ，它返回一个C字符串，其中包含指定为参数的环境变量的值。

Example:

例：

    Function call:
getenv ("PATH");
Output:
Specified the environment variable (PATH)

C ++代码演示getenv()函数的示例 (C++ code to demonstrate the example of getenv() function)

// C++ code to demonstrate the example of
// getenv() function
#include <iostream>
#include <cstdlib>
using namespace std;
// main() section
int main()
{
char* path_string;
// getting path
path_string = getenv ("PATH");
if (path_string!=NULL)
cout<<"The current path is: "<<path_string<<endl;
return 0;
}

Output

输出量

RUN 1: (Compiler: https://www.onlinegdb.com/ (c++))
The current path is: /opt/swift/swift-5.0-RELEASE-ubuntu14.04/usr/bin/:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
RUN 2: (Compiler: https://www.jdoodle.com/online-compiler-c++/)
The current path is: /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/opt/isCOBOL2019R1/bin:/opt/cs/artifacts/Release/bin

Reference: C++ getenv() function

参考： C ++ getenv()函数