global variable for getenv() ?

tags:

c
glibc

views:

answers:

+2 Q:

global variable for getenv() ?

+5 A:

char **environ is NULL-terminated array of strings, so you should try:

extern char **environ;
char **p;
for (p = environ; *p; p++) {
    printf ("%s\n", *p);
}

In other words, environ[0] is pointer to first env variable, environ[1] to second etc. Last element in environ array is NULL.

el.pescado 2010-06-27 14:27:37

And there's no guarantee that the list of variables is any particular order, and in some (unusual) circumstances, there might be two entries for a single variable. It used to be the case that the environment was also passed into POSIX-ish programs if you used `int main(int argc, char **argv, char **envp)` for the main function declaration. However, neither the 2003 nor the 2008 standard mentions this possibility, so I guess it is not guaranteed. MacOS X still supports it, and so probably do most variations of Unix (it was documented for 7th Edition Unix in 1979).

Jonathan Leffler 2010-06-27 15:25:47