How to use environment variable in a C program

Question

I need to know a way for use environment variables in the C programming language. How can I use and read them?

For example, read an environment variable or take the value of an environment variable and load it in another variable.

Solution 1

You can use following functions -

char * getenv (const char *name)-returns a string that is the value of the environment variable name.

char * secure_getenv (const char *name)

Read about some more functions here -http://www.gnu.org/software/libc/manual/html_node/Environment-Access.html#Environment-Access

Solution 2

Use the getenv function from stdlib.h. That's it!

Solution 3

getenv:

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[])
{
    char* my_env_var = getenv("MY_ENV_VAR");

    if(my_env_var)
        printf("Var found: %s", my_env_var );
    else
        printf("Var not found.");                

    return 0;
}