getenv

 

C

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Program support utilities

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abort exit quick_exit (C++11) _Exit (C++11)	atexit at_quick_exit (C++11) EXIT_SUCCESSEXIT_FAILURE
Communicating with the environment
system	getenv
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Defined in header <stdlib.h>
char *getenv( const char *env_var );

Searches for an environmental variable with name env_var in the host-specified environment list and returns information associated with it. The set of environmental variables and methods of altering it are implementation-defined.

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.

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 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 <stdio.h>
#include <stdlib.h>
 
int main(void)
{
    char *env_p = getenv("PATH");
    if (env_p)
        printf("PATH = %s\n", env_p);
}

Output:

PATH = /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

See also

C++ documentation for getenv