1 /*-------------------------------------------------------------------------
4 * unsetenv() emulation for machines without it
6 * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
7 * Portions Copyright (c) 1994, Regents of the University of California
11 * $PostgreSQL: pgsql/src/port/unsetenv.c,v 1.4 2004/12/31 22:03:53 pgsql Exp $
13 *-------------------------------------------------------------------------
20 unsetenv(const char *name)
24 if (getenv(name) == NULL)
28 * The technique embodied here works if libc follows the Single Unix
29 * Spec and actually uses the storage passed to putenv() to hold the
30 * environ entry. When we clobber the entry in the second step we are
31 * ensuring that we zap the actual environ member. However, there are
32 * some libc implementations (notably recent BSDs) that do not obey
33 * SUS but copy the presented string. This method fails on such
34 * platforms. Hopefully all such platforms have unsetenv() and thus
35 * won't be using this hack.
37 * Note that repeatedly setting and unsetting a var using this code will
41 envstr = (char *) malloc(strlen(name) + 2);
42 if (!envstr) /* not much we can do if no memory */
45 /* Override the existing setting by forcibly defining the var */
46 sprintf(envstr, "%s=", name);
49 /* Now we can clobber the variable definition this way: */
53 * This last putenv cleans up if we have multiple zero-length names as
54 * a result of unsetting multiple things.