std::getenv
<cstdlib>
Searches the environment list provided by the host environment (the OS), for a string that matches the C string pointed to by env_var and returns a pointer to the C string that is associated with the matched environment list member.
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.
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.
Modifying the string returned by getenv invokes undefined behavior.
Contents
[edit] Parameters
[edit] Return value
Character string identifying the value of the environmental variable or null pointer if such variable is not found.
[edit] 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.
[edit] Example
#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