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#include <stdio.h>
#include <stdlib.h>
// for: char *getenv(const char *name);

int
main(int argc, char *argv[])
{
    // print all program arguments
    for (int i = 0; i < argc; ++i) {
        printf("argv[%d] = %s\n", i, argv[i]);
    }

    // print value of an environment variable
    printf("Variable %s = %s\n", "USER", getenv("USER"));
    printf("Variable %s = %s\n", "FOO", getenv("FOO"));
}