NAME
putenv() — change or add value to environment
SYNOPSIS
#include <stdlib.h>
int putenv(const char *string);
DESCRIPTION
string
points to a string of the form
name=value.
putenv()
makes the value of the environment variable
name
equal to
value
by altering an existing variable or creating a new one.
In either case, the string pointed to by
string
becomes part of the environment,
so altering the string changes the environment.
The space used by
string
is no longer used once a new string-defining
name
is passed to
putenv().
EXTERNAL INFLUENCES
Locale
The
LC_CTYPE
category determines the interpretation of characters in
string
as single- and/or multi-byte characters.
International Code Set Support
Single- and multi-byte character code sets are supported.
DIAGNOSTICS
putenv()
returns non-zero if it was unable to obtain enough space via
malloc()
for an expanded environment, or if an invalid multibyte character
sequence was encountered in the string argument; otherwise it returns zero.
ERRORS
putenv()
fails under the following conditions:
- [ENOMEM]
There is insufficient space to expand the environment.
- [EILSEQ]
An invalid multibyte character sequence was encountered in the string
argument.
WARNINGS
putenv()
manipulates the environment pointed to by
environ,
and can be used in conjunction with
getenv().
However,
envp
(the third argument to
main)
is not changed.
This routine uses
malloc()
to enlarge the environment (see
malloc(3C)).
After
putenv()
is called, environmental variables are not in alphabetical order.
A potential error is to call
putenv()
with an automatic variable as the argument,
then exit the calling function while
string
is still part of the environment.
STANDARDS CONFORMANCE
putenv(): AES, SVID2, SVID3, XPG2, XPG3, XPG4
Printable version
