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