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/* Replacement for a missing setenv.
** Written by Russ Allbery <>
** This work is hereby placed in the public domain by its author.
** Provides the same functionality as the standard library routine setenv
** for those platforms that don't have it.
#include "config.h"
#include <stdlib.h>
#include <string.h>
setenv(const char *name, const char *value, int overwrite)
char *envstring;
if (!overwrite && getenv(name) != NULL)
return 0;
/* Allocate memory for the environment string. We intentionally don't
use concat here, or the xmalloc family of allocation routines, since
the intention is to provide a replacement for the standard library
function which sets errno and returns in the event of a memory
allocation failure. */
envstring = malloc(strlen(name) + 1 + strlen(value) + 1); /* __MEM_CHECKED__ */
if (envstring == NULL)
return -1;
/* Build the environment string and add it to the environment using
putenv. Systems without putenv lose, but XPG4 requires it. */
strcpy(envstring, name); /* __STRCPY_CHECKED__ */
strcat(envstring, "="); /* __STRCAT_CHECKED__ */
strcat(envstring, value); /* __STRCAT_CHECKED__ */
return putenv(envstring);
/* Note that the memory allocated is not freed. This is intentional;
many implementations of putenv assume that the string passed to
putenv will never be freed and don't make a copy of it. Repeated use
of this function will therefore leak memory, since most
implementations of putenv also don't free strings removed from the
environment (due to being overwritten). */