std::getenv

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Program support utilities
Defined in header <cstdlib>
char * getenv( const char * env_var ) ;

Searches the environment list provided by the host environment (the OS), for a string that matches the C string pointed to by env_var

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()

(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()

(since C++11)

Modifying the string returned by getenv invokes undefined behavior.

Parameters

env_var - null-terminated character string identifying the name of the environmental variable to look for

Return value

Character string identifying the value of the environmental variable or null pointer if such variable is not found.

Notes

On POSIX systems, the environment variables are also accessible through the global variable environ, declared as extern char** environ; in <unistd.h>, and through the optional third argument, envp, of the main function

Example

Run this code
#include <cstdlib>
#include <iostream>
 
int main()
{
    if (const char* env_p = std::getenv("PATH"))
        std::cout << "Your PATH is: " << env_p << '\n';
}

Possible output: 

Your PATH is: /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games

See also

C documentation for getenv
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